A large quake prompts the commander to call for an evacuation of all ORCA personnel under the age of 18. Dr. Hellegren is putting the Synchronium together when Kal demands that he be made the ruler of Neri's island as he was promised, Hellegren again brushes off Kal and has him escorted back to his room. Anxious to get the Synchronium back from Dr. Hellegren, Neri goes to get Jason. He is out on a dive mission with Sallyanne, and when Neri surfaces Sallyanne is there to see her. Angry about the way he is being treated by Dr. Hellegren, Kal attempts to steal a piece of the Synchronium, he is quickly caught by UBRI guards and taken back to his room. Back on ORCA, Sallyanne is introduced to Neri and Mera and plans are made to recover the Synchronium. Getting away during the confusion surrounding the evacuation, the kids are able to make it to UBRI's pier on the mainland. However, they are soon spotted by Kellar and are left tied (Dr. Hellegren taking Lena with him) up as the UBRI vessel h

Jason and Brett round up their friends to help rescue Charlie, but Jason must also tell them the truth about Neri. Dianne destroys all of her research on Neri after Commander Lucas tells her that he will have to file a report on Neri. The kids infiltrate the UBRI command post and are able to release the net and free Charlie. A blood test done on Neri indicates that she is not human. Dianne convinces Commander Lucas not to file his report. Leaving with Charlie on his annual migration, Neri tells her friends to watch for her return.

Neri receives a message from Mera in a dream warning her that time is running out. Neri goes to ORCA where she warns Dianne that UBRI's development must be stopped. Kellar tells Hellegren of her suspicions about Lena, but he won't listen to her and tells her to not to question his daughter. Jason is forced to tell Lena all about Neri and their search for the Synchronium. Dr. Hellegren orders the construction of ORCA City to be sped up by increasing the yield of the explosives. Cass is sent to a psychiatrist to help her understand her dreams, what she remembers however is quickly reported back to Dr. Hellegren who observes her next session. Cass returns to ORCA with a restored memory and demands to know the truth. She is taken to meet Neri and promises to keep her a secret and aid in the search for the Synchronium. With evidence of his daughters actions, Dr. Hellegren confronts Lena, she admits what she's been doing and leaves home after he says she is no longer his daughter. Kal experi

Kellar shows Dr. Hellegren the footage she took of Kal on the sandbar, he quickly recognizes who Kal is and wants to capture him. After another of Kal's outbursts at Jason, Neri tells him to change his attitude or leave the island, Kal chooses the latter. A causal remark by Dave Hartley to Dianne has Brett thinking he may be interested in her. Brett recruits Benny to write a love note hoping to get the pair together (for his own selfish reasons mind you). Unfortunately, Jason inadvertently gives the note to Sallyanne who thinks Jason has finally taken notice of her. When he tells her of the mistake, Sallyanne is crushed. Brett tries to end the fiasco by throwing out the note but is is retrieved by Delores, a girl he's been hounded by all day. Kal is caught by Dr. Hellegren and taken back to UBRI headquarters where Hellegren begins the process of convincing Kal to trust him. Worried about what has become of Kal, Neri, Brett and Jason search the island for him.

The effects of the new ""Winston Seth"" fault line are being felt all around the Pacific Rim as evacuations on ORCA are taking place. Lena locates the final piece of the Synchronium. Mera grows more suspicious of Kal's frequent disappearances but Neri once again defends his behaviour. After Sallyanne confronts Jason, Lena tells him that he should tell Sallyanne about Neri as she is his only close friend who doesn't know. He kids venture inland to recover the Synchronium, UBRI is also searching in the area but it is Neri who recovers the final piece. Neri gives the Synchronium piece to Jason to take to the underwater cave. Kal observes the pair leaving and discovers the location of the cave. He quickly reports back to Dr. Hellegren who, after dismissing Kal's request to have his side of their bargain upheld, sets out to recover the Synchronium. As Kal is bringing the pieces to the surface for Hellegren, Charlie warns Neri about what is going on, but when she gets to the cave, the Synchron

New monitoring equipment allows Dianne and Winston to hear Neri's communications with Charlie but when the tag on Charlie stops working Dianne must go out and replace it. Using the songs of Charlie and Neri, Dianne and Winston are able to attract Charlie to their location. Dianne runs out of oxygen while diving but is rescued by Neri who is forced to reveal herself to Dianne and Winston in the process. When Dianne's research is faced with being shut down, Neri replaces the lost transmitter on Charlie enabling her research to continue.

Neri continues to teach Kal about feelings. Cass is still having her dreams about her time on Neri's island and now remembers Brett being there. Lena overhears her father and Kellar talking about their plans for creating a news bulletin to lure some of the kids from ORCA to an island to find out exactly what they know about the alien device. Jason is uneasy about his helicopter flight test and is unable take the controls. Kal searches the spaceship for a gift left to him by his parents. Benny and Brett arrive and find him playing a strange musical instrument and crying, Brett explains to Kal why people cry. Seeing the news bulletin created by UBRI, Brett and Neri head off to the remote island looking what they believe to be another piece of the Synchronium. Lena arrives on ORCA to warn the Bates brothers about the trap but she is too late to stop Brett, she does find Jason and warn him. Needing to get to Brett and Neri quickly, Jason goes on another helicopter test with Morgan and dive

The cadets' exam results are in and after looking at her's, Sallyanne tells Jason he would be better off with another partner. Mera reveals to Neri and her friends that Charlie's song is the trigger that activates the Synchronium. Kal overhears this and quickly goes to tell Dr. Hellegren. Hellegren meanwhile has to contend with his financiers who are anxious for results. Mera is taken to ORCA and introduced to Benny, Cass and Lena. Neri and Mera talk Lena into stealing the key her father wears around his neck—it is the only way to gain access to the Synchronium that UBRI has. Outside the Hellegren home, Kal makes a surprise appearance wanting to help. After Lena gets them into the house and Neri is about to get the key, Kal intentionally knocks over a vase waking Hellegren. They are all able to escape but do not get the key. Disappointed about her scholastic performance so far, Sallyanne wants to quit but decides against it after saving Jason when a bulkhead is breached.

Budds The growing frequency of the seismic tremors causes Commander Wellington to call for voluntary evacuations of ORCA personnel. Cass tells Morgan to ""drop dead"" when Morgan gets after Jason for wanting to skip a survey dive. Jason's dive with Morgan ends abruptly when Morgan is stung by a stonefish, requiring her to be rushed back to ORCA. Cass feels guilty for what she said to her sister earlier. Sallyanne tries to talk to Jason about how she feels about him but he dismisses her to join his friends who are preparing to intercept the Synchronium transfer from Mr. Lee to Dr. Hellegren. Brett stows away on the UBRI vessel and when the are out at sea, he disables the craft and steals the Synchronium piece. Brett jumps overboard where Neri and Mera are waiting just as the Coast Guard arrives to board the UBRI vessel—Benny faxed them to tell them about UBRI's involvement with Opal smuggling. Having losing another piece of the Synchronium, Dr. Hellegren tells Kal that his most important

Asleep on her island late at night, Neri has a vision of her mother, she tells Neri that it is ""her time"" but Neri admits that she is afraid of what is to come. On the Ocean Planet, Shersheba is taken prisoner by Garron, on Malakat's order, upon arriving. She tells Garron that she has brought the cure to the virus—but will only release it if she is recognized as their leader. Neri stops at ORCA to discuss with the Bates family her plans to go to the pyramid. Neri asks Helen, who has been in contact with the underwater pyramid, to ask it to allow her to enter the pyramid undetected. Through Helen, the pyramid directs Neri to the ""cave of light"" in the outback. In the underwater pyramid, Malakat orders the pyramid to destroy ORCA, but soon after Neri and Jason arrive and start the process to destroy the pyramid. Just as they are about to finish, Shalamorn enters the central chamber and retakes control of her pyramid.

Jason and Brett steal a pump from UBRI supplies on ORCA so they can pump out the spaceship. Cass and Brett trade practical jokes but when they team up to get Cass's sister Morgan, they also catch the Commander in their soapy trap. Jason is teamed up with Sallyanne for a training exercise, but their first drill does not go well. With the spacecraft pumped out, Neri and Jason enter the ship. They are joined by Brett, who has been scrubbing the floors on ORCA for his role in the practical joke on Morgan, and the trio come across a person in a sealed chamber, still alive

Neri moves the Synchronium piece to her secret underwater cave to keep it safe. Benny's father chastises him for spending time with Brett and Cass instead of studying. Cass finds a young boy on ORCA who swam to ORCA from the ship that was taking him and his family home after they were refused refugee status, she keeps him a secret and brings him food. Brett and Benny go in search of sunken treasure but when a valuable piece of equipment falls overboard, Benny goes after it and runs out of oxygen. Charlie calls Neri to rescue him revealing to him her presence. Benny lies to the commander about the incident to keep Neri a secret. Cass' stowaway is discovered and he is turned over to immigration officials. Lena gains access to her father's files about Neri.

A trip to ORCA prompts a discussion between Neri and Kal about feelings. Cass is beginning to remember about her time on Neri's island in her dreams. Brett takes Benny to the island to see Neri and Kal and Jason arrives soon after having discovered the location of another piece of Synchronium deep in the ocean. Neri is anxious to retrieve it and sets out by herself. The boat taking Brett and Benny back to ORCA breaks down, and with strict instructions not to go to ORCA, Kal abandons them in the middle of nowhere. Fortunately, Charlie alerts Neri, who was unsuccessful in her attempt at retrieving the Synchronium, and she comes to their rescue. Back on ORCA Brett is hassled by Moose, a bully who demands his new satellite navigation unit. With Jason and Brett assisting her, Neri retrieves the Synchronium from the ocean depths just moments before UBRI arrives on the scene. Brett is again confronted by Moose but Kal, acting on the lesson he received on loyalty after abandoning Brett and Ben

Brett tries unsuccessfully to get Kal to come out of the spaceship. Dianne is granted a tribunal hearing to voice her concerns about the effects UBRI's construction is having on the fault line. During the hearing a tremor hits causing panic on ORCA and causing Charlie to beach himself. Neri recruits her friends on ORCA to try and rescue him. Jason leaves his post to help out and Sallyanne must cover for him when the Commander asks her where he is. The tribunal allows UBRI to continue their construction, but without blasting. Kal comes to ORCA looking for Brett but ends up talking with Sallyanne since everyone else is helping with Charlie. Needing additional help to free Charlie, Jason recruits Winston who helps place a sling under Charlie so that he can be towed off the sandbar. Returning to the island, Kal asks Neri why he wasn't asked to help with Charlie, unhappy with her answer, he walks away. On a secluded sandbar, Kal is observed and photographed by UBRI.

Neri has Kal promise not to leave the island again. Lena uses HELEN to locate another piece of the Synchronium. Mera appears to Neri to again warns her that time is running out. The next day, Neri and Kal are on ORCA, but when asked to pinpoint the landing area of the Synchronium, Kal says he cannot. Kal tells Neri he is going back to the island to have a swim and think about problem but he instead goes to see Dr. Hellegren to tell him about the new piece. Hellegren isn't anxious to sent UBRI forces after it, instead preferring to let the kids find it and then take all the pieces at once after Kal discovers where they are hidden. Lena does her best to pinpoint the location of the Synchronium, but must use more of HELEN's resources to do so. Unfortunately an earthquake hits at that moment and the Commander quickly discovers the extra strain on HELEN when he is unable to access HELEN. As punishment for their actions, Lean, Cass, Brett, and Benny are assigned to clean-up detail—with Morga

Jason takes Neri and Mera swimming off the ORCA platform. Mick finds out and heads out on a jetski, he falls off and must be rescued by the girls. Neri helps Mick with his reading, he in turn joins the others in keeping Neri and Mera a secret. Forsythe tries to get access to Dianne's research and cripples HELEN in the process, in the confusion Lyselle sees Mera in the coridor and reports back to Dr. Hellegren that Neri and Mera are on ORCA. Winston, receiving strange signals from Neri's island, goes to investigate and meets two strangers, but back on ORCA he says his trip was uneventfull.

Brett locates another piece of Synchronium but interrupts Jason's training exercise to tell him the news. UBRI has also located the piece and mount an effort to retrieve it. Lena is back on ORCA looking for clarification about her father, she learns nothing from Brett but does meet Kal. Jason, Brett, and Neri go after the second piece of Synchronium, it is far inland and they must go by camel. Arriving after UBRI, who have already recovered the Synchronium, the trio is spotted and pursued by Kellar who they are able to elude on their sure-footed camels. Dr. Hellegren begins studying the piece of Synchronium and discovers that it generates a tidal force.

Winston is excited about the arrival of Camilla Sabato (Robyn Gibes) to ORCA, she is a science writer but more importantly, a close friend. Winston gives her a tour of ORCA but afterward Brett catches her making a secret transmission to Dr. Hellegren telling him that she will be looking for information about his ""Ocean Girl."" Brett informs Dianne and Winston who see that Camilla leaves ORCA. Kal finishes at the top of his class in a fitness competition, he returns to the island to tell Neri but finds her once again preoccupied with Jason. Kal's jealousy surfaces again and after telling Jason that he is no longer welcome on the island, he moves back into the spaceship. Neri is concerned about the condition of a nearby coral reef, she and Jason go to film the site (Jason skips out on a party that Sallyanne asked him to) hoping to gather evidence to prove that ocean life is being destroyed by UBRI's construction of ORCA City. A large earthquake strikes, opening the fault line near ORCA.

Prior to leaving on the final survey mission, Dianne learns Commander Byrne has assigned Froggy, Zoe, Joanne, Rocky and Kimberly to her crew. Forsyth hides a transmitter on the boat to allow UBRI to follow it. UBRI divers are dispatched to apprehend Neri and Mera and in their struggle with the UBRI divers, Neri and Mera are caught by the boat's cameras for all to see, revealing their existence to everybody on board. Responding to Mera's call for help, Charlie intervenes allowing the girls to escape, it's the first time Mera has been able to talk to Charlie. After being told about Neri and her sister, the kids all agree to keep the secret, except for Mick who just says that he'll ""think about it.""

Neri leaves ORCA intending to save Mera and Charlie by giving herself up to UBRI. Brett chases after her, gets into an accident with a UBRI boat and is saved by Neri. Sam destroys his remaining records of the titanium deposit. Winston continues to secretly meet with the two strangers. Unable to bring the girls back to the island, Winston takes the two strangers to ORCA where they tell Neri and Mera that they have come to take them back to the Ocean Planet, their home. Vanessa helps Mick with his reading and defends him when Commander Byrne accuses him of slacking off.

Neri and Mera make the decision to return to the Ocean Planet and convince Diane that her research must continue. Froggy fixes HELEN, with a little help from Damien. Commander Byrne has Forsythe arrested when HELEN identifies him as the sabateur. The kids take care of Liselle, keeping her from contacting UBRI. Neri and Mera are taken back to the island, with Winston, Mick and Zoe acting as decoys to keep UBRI away. Final goodbyes are said as the girls board the spacecraft for home but after the ship leaves, one person has stayed behind. Neri says she must stay to ""finish father's work.""

Brett talks Jason and Neri into looking for a way into the spacecreaft they found buried on Neri's island  their search is unsuccessful. Brett and Benny meet Cassandra, a new arrival from ORCA's sister station near Florida. Cass takes out a sailboat, but with a storm coming and a damaged sail, she seeks shelter on Neri's island. The following day Neri finds an entrance to the spaceship that was uncovered by the storm. When Jason and Brett come to the island, Cass sees them with Neri before fixing the sail on her boat and heading back to ORCA. Distracted by the sight of Neri in the water ahead of her, Cass is struck by the boat's boom and is knocked unconscious. Back on ORCA an anxious Jason and Brett discover Cass has amnesia and cannot rememeber what happened to her. Jason tells Brett to become friends with Cass to keep her from telling about Neri if she gets her memory back. Dr. Hellegren goes to visit his daughter at her boarding school, she pleads with him to be allowed to spend h

Brett and Jason are out testing a new diving suit when Jason encounters a strange bright light while under water, the pair quickly leave and head off to see Neri. Back on ORCA, Winston is puzzled by a magnetic anomaly on his scans of the ocean floor, even more strange is that the anomaly is in the shape of a perfect square. Dianne announces that she is going to pursue the vacant position of ORCA Commander. Jason matches the location of Winston's magnetic anomaly to where he saw the strange lights, Neri is also intrigued by the region prompting a closer investigation of the region. Neri swims out to the sight with Jason and Winston following in the minifin, ORCA's new underwater submarine. What they find surprises everyone—a huge underwater pyramid. Meanwhile, at Praxis headquarters (Preventative Response And eXtraterritorial Intelligence Service), agents Jake Shelby and Elly Hauser are dispatched to Egypt where reports suggest signals from outerspace are being received.

As the kids are preparing for their shore leave to Port Jackson, Neri makes a surprise visit that forces Jason and Brett to take her with them. Damien invites Neri to see a movie but the experience frightens her and she runs off. On her own, Neri meets a young boy and helps him retrieve a stolen bracelet. Returning to ORCA, Jason and Lee find themselves alone but Commander Lucas' arrival makes for an awkward moment. Neri asks Brett what kissing is like and when he suggests she try it, she does—with Damien. Dianne and Winston come to the conclusion that Charlie is actually communicating with the small animal that accompanies him (Neri) but Dianne is not happy by Jason's lack of interest in the success of her research.

Hoping to keep Kal from making any return trips to ORCA, Jason suggests to Neri that she show him around the spaceship which he has been interested in. Winston's inability to swim is made an issue of by Kellar and UBRI, threatening his job on ORCA as they hope to replace him with one of their own. Fortunately, Benny discovers a provision is the regulations forcing the commander to give Winston a week to meet the qualifications. Neri brings Jason and Brett back to the ship where she and Kal have made a discovery. An interface with the ship's computer gives Neri access the ship's log written by Kal's mother. She explains to the group about a mission requiring the assembly of nine pieces of ""Synchronium"" which once put together will have the power to heal the Earth's oceans. Neri asks Jason and Brett to help her look for the Synchronium but they must no tell anyone else. Believing that Neri is close by to assist him, Winston passes his swimming test.