After sneaking some students off the island and to the mainland, the Lab  Rats accidentally leave Spin and Bob behind and must retrieve them  before Donald finds out. Meanwhile, Donald tries on Chase's mission suit  and he and Leo scramble to get it off before Chase gets home.

Left Behind

William Brent

Spencer Boldman

Kelli Berglund

Tyrel Jackson Williams

Hal Sparks

Julia Miranda

Under Siege

Bionic Rebellion (2)

Sebastian has secretly formed an evil rebellion to get revenge on the  Lab Rats for destroying his father. Meanwhile, Leo is trapped with the  other bionic people who also want revenge, but Leo manages to convince  Spin and Bob to help him, and, in the end, Sebastian is defeated, his  rebellion is brought down, and he and his comrades are taken to a  facility. Meanwhile, Donald successfully convinces the others that he  has the best interest for them at heart while Adam still blames Chase  for everything that happened after the rebellion is over.

Bionic Rebellion (1)

When suspicious events happen overnight on the bionic island, everyone  is convinced a new threat has emerged. However, this threat is revealed  to be Leo, when his bionics glitch because Douglas never gave Leo a  capsule.

Adam brings a dog back to the island and Douglas reveals that it's his  old dog, Otis, who Douglas made bionic in order to save his life when  Otis was injured. Chase turns out to be allergic to dogs as he starts  sneezing, so Douglas says that Otis has to leave, but he and Adam  actually hide the dog. Meanwhile, Leo gets a new smartphone application  assistant named Shelly, with whom he has fallen in love.

Bionic Dog

The Lab Rats are on a mission to save people from a wildfire; when the  people start to chant Adam, Bree, and Chase's names, Leo gets jealous  and wants to become known. Douglas gets put in charge to develop a new  technology for the academy, but can only come up with things that can  hurt the students.

Mission Mania

Adam and Chase each lead their own student groups against each other in a  series of simulated exercises that will evaluate both student and  mentor performance. However, after Chase's group fails at defeating the  exoskeleton and defusing a virtual bomb, Chase decides to find a way to  cheat and win.

Simulation Manipulation

When Leo is injured during a mission, Tasha rushes to the academy to  take care of him. After finding out what happens on missions, she bans  Leo from joining any more missions, but he disobeys her and goes on a  mission with the rest of the team. When Tasha finds out, she kicks Leo  off the team and tells him that he is moving back to Mission Creek.

Forbidden Hero

Chase and Douglas reanimate a prehistoric sea spider. It escapes and  bites Adam, which poisons him. It then grows and becomes 50 feet long  due to growth hormones that had been given to it by Douglas. Everyone  tries to stop the spider so they can create a cure for Adam.

Spider Island

Douglas finds out that there is a student named Kate with the Commando  App. Chase tries to activate her Commando App, named Spikette by  Douglas, so he can research her. When he starts fighting with Adam, she  activates her Commando App and thinks Chase is her baby. While she  destroys the bionic academy, Bree forces Chase to activate his Commando  App by embarrassing him so he and Kate can battle. Unfortunately, he  teams up with her. Douglas gives Bree a Commando App and she and Kate  begin battling each other. Bree wins and Douglas extracts Kate's chip.  Chase apologizes to Kate and finds out that Douglas replaced her  Commando App with sonic screaming.

Spike vs. Spikette

Chase and Donald have invented a new technology that takes in energy  from any environment. Chase feels that he does not get his share of  spotlight when Donald sells the product without his approval. Meanwhile,  Kaz comes to the bionic academy to get powers, bringing Oliver with  him.

Lab Rats vs. Mighty Med

Donald's top scientist, Dr. Ryan, arrives to test Chase's invention. The  two of them dislike each other and don't get along. When Donald puts  Dr. Ryan in charge of the space elevator, Chase immediately gets  jealous. Donald then makes Chase Dr. Ryan's assistant. Dr. Ryan puts  Chase in charge of screwing in the lug nuts, but Chase refuses, and Dr.  Ryan builds the space elevator without Chase. The day of the launch,  Chase performs a bionic scan of the elevator and finds a major braking  flaw on the elevator.

Space Elevator

Douglas tells the group that his old college ex-girlfriend, a film  director named Giselle, will be making a film titled Bionic Action Hero  based on all of them and starring an up-and-coming actor named Troy  West. Giselle and Troy visit the island to learn about the bionic team.

Bionic Action Hero (1)

Bionic Action Hero (2)

Adam, Bree, and Chase are looking for Leo because he is late for  training and find out he is in Mission Creek because Janelle threatened  to break up with him. S-1 shows up unexpectedly and shocks everyone. She  came to the island because, like everyone else, her memory is blank,  but has continuing flashbacks of Krane.

One of Us

Douglas creates a device that makes any bionic human as smart as Chase.  After Douglas tests it on Bob, Bob starts spending time with Chase. This  leaves Adam in envy. Meanwhile, Perry made the island officially her  own, which makes Bree and Leo angry at her.

Bob Zombie

Donald gives Eddy a human body and replaces his disrespectful  personality to make him nicer. Perry restores his old personality, and  he attempts to harm the students.

Human Eddy

Leo just finishes his movie marathon while everyone else is frustrated  because they have nothing to do on Halloween. Bob intentionally stays  behind while the other students are away with Davenport to a museum.  Perry says she's going to another island across from theirs, but Douglas  says no because it's deserted and has been uninhabited for years. When  Douglas leaves, the group decides to go anyway.

The Curse of the Screaming Skull

Donald tells the group that the president has decided to host an award  ceremony because they have completed their one-thousandth mission and  Leo wants his recognition, but it's only for the original members.  Disappointed, Leo forms his own team with S-1, who calls herself Taylor  now, and Logan.

On the Edge

Tasha arrives on the Bionic Island informing everyone that she has  tickets to a big football game of the Pioneers (mascot of a college that  she went to) vs Vikings (mascot of a college that Perry went to) and  Perry arrives stating that she has been trying to score tickets for  weeks but it was sold out. When she asks Tasha if she has any tickets,  Tasha lies saying that she hasn't. When they are about to enter the  game, Perry eventually finds out the truth, she becomes furious and  destroys the tickets which causes Leo, Donald, and Tasha to try to get  new tickets competing against her in The Ultimate Tailgate Challenge,  hosted by NFL former linebacker Willie McGinest. Meanwhile, Bree  attempts to achieve her college experience by fitting in with a couple  of college students (who are football fans) and attempting to use her  bionics to impress them.

Ultimate Tailgate Challenge

Everyone is shocked when Douglas introduces a fourth bionic sibling  named Daniel who’s been living a normal life with an adopted family.  Daniel later comes to the academy to meet his father, uncle, and  cousins. After Daniel's bionics are accidentally activated by the Lab  Rats, Donald and Douglas find out what happened they have to come clean  to Daniel about his power-replicating abilities. Daniel also finds out  that his cousins are actually his biologic siblings. Filled with anger,  Daniel goes out for air on the beach, where Leo and him have a  conversation about Douglas. Not too long after, Daniel, using Leo's  abilities, accidentally causes a leak in the hydro-loop's fuel tank.  After Adam and Daniel combined their powers to stop it, Douglas  apologizes to Daniel for lying and Daniel decides to give Douglas a  second chance.

And Then There Were Four

In the middle of a massive heat wave, the whole family is going to space  to see Donald's space colony, called "Davenportia". Adam annoys Chase  while Chase tries to give his safety instructions and accidentally  blasts them into space. After leaving the solar system, they initiate  hyper-speed and land on the planet Lithios. In the dome, it's discovered  that Perry sneaked her way in with the rest of the colonists.

Space Colony

Donald and Douglas reveal that they have built an upgrade for all the  students bionics, except for Leo's. But the upgrade doesn't work on  Adam, Bree, and Chase because their systems are older. Adam, Bree, and  Chase are therefore left at their level, while all the students are much  more powerful. Meanwhile, Daniel is brought to the Academy because he  had been using his bionics in the outside world. Douglas decides to  enroll Daniel at the Academy, and he makes Leo his mentor. Leo steadily  tries to teach Daniel, but Daniel proves to be unteachable, so Leo gives  him the upgrade as well. The students steadily start to vanish,  including Daniel. Giselle Vickers, Douglas' old girlfriend, is revealed  to have captured them. Daniel sends a video message to the Island,  requesting help.

The Vanishing (1)

Giselle reveals she dug up Marcus from Douglas' old lair and rebuilt  him, piece-by-piece. Marcus wants revenge on Douglas for leaving him to  die. Everyone rushes Giselle and Marcus, but Marcus knocks everyone  unconscious. Donald and Douglas are tied together in chairs, while Adam,  Bree, Chase, and Leo are put in the chamber with the students, while  Daniel is pulled out.

The Vanishing (2)

Leo is an ordinary teenager who has moved into a high-tech "smart'' house with his mother, inventor stepfather and Eddy, the computer that runs the house. Leo's life becomes less ordinary when, one day, he discovers a secret underground lab that houses three experiments: superhuman teenagers. The trio -- Adam, the strong one, Bree, the fast one and Chase, the smart one -- convinces Leo and his parents to let them leave their lab and join Leo at school, where they try to fit in while having to manage their unpredictable bionic strengths. As Leo figures out a way to keep his new pals' bionic abilities a secret, they help him build self-confidence.

Left Behind

Seasons4

Season 4 Episodes24

Cast5

Crew2

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Episode Summary