When a pest controller is attacked in the London Underground and landed in hospital poisoned with venom, Cutter, Claudia and the team investigate and discover the Underground is infested with giant, Carboniferous spiders. Cutter and the team soon learn that the true culprit is not the spiders, but a giant centipede, and they are sent in a race against time to get the centipede's venom after it poisons Stephen. Meanwhile, Connor gets thrown off the team after telling two of his friends about the Anomalies, and attempts to earn the team's faith back in the fight against the giant centipede. At the same time, Cutter's suspicions that Helen is alive on the other sides of the Anomalies increases.

The team go to investigate a flunctuating Anomaly signal at a seaside village, and Matt and Abby struggle to contain a fast and deadly Labyrinthodont's rampage while Connor tries to uncover the secret behind the fluncuating Anomaly signal. Meanwhile, Emily has been captured by Ethan, and Matt attempts to track and save her before it's too late.

Eight years after his wife Helen mysteriously disappeared, Nick Cutter and a team of several others investigate reports of a large animal in the Forest of Dean, and discover that mysterious Anomalies in time and space are appearing and allowing prehistoric creatures to cross into the present day.

When an Anomaly opens at a theatre, a group of mysterious Anomaly travellers come through, followed by fast and deadly Tree Creepers. Meanwhile, Connor helps Philip design a new security system for the ARC, but it goes horribly awry and sends the ARC into lockdown, and time is running out for Connor to free Rex and Philip before the system suffocates them.

Matt, Connor and Becker investigate an Anomaly at a secondary school and struggle to save the remaining students from deadly, venomous Therocephalians. Meanwhile, Philip decides to have the ARC's captive creatures including Rex euthanized, prompting Abby to try and smuggle them to safety before it's too late.

The team attempt to track a giant, underground insectoid predator from the future, and there is something about the creature that Matt isn't telling the team. Meanwhile, Philip shows Connor the true purpose behind New Dawn, and Abby becomes more suspicious of Matt and grows closer to discovering his secret, while Lester struggles at the ARC to make a good impression to Ms. Reece of the Cabinet Office for a knighthood.

When a Navy submarine in the North Sea discovers a giant underwater Anomaly, Matt, Connor and Abby join the Navy crew aboard, but things go awry when the submarine is pulled through the Anomaly into a prehistoric sea inhabited by giant pliosaurs. The team subsequently attempt to get the submarine back through the Anomaly to their time, while Lester struggles to stop an Admiral from nuking the Anomaly and potentially altering history.

The team are called in to investigate when a lifeguard is eaten by a Mosasaur at a swimming pool. Cutter discovers that they are dealing with a mobile Anomaly when the Mosasaur and the lifeguard's vomited remains appear at a reservoir and a cellar floods and is invaded by a Hesperornis. The rest of the team also learn that Helen is alive and on the other side of the Anomaly, and so Cutter is forced to go through and confront the woman his wife has become.

Connor builds the team a new device designed to detect and locate new Anomalies, but the team become doubtful that the device works when it detects no Anomaly when a paintballer is torn to shreds in the luxurious Blue Sky Park resort. The team soon learn that the mysterious predator stalking the Park is a powerful and deadly sabre-toothed cat, and the race is on to find who is harbouring and protecting the sabretooth before it kills again.

Helen Cutter directs the team to an Anomaly at a football stadium and escapes through, leaving behind a flock of Dodos. The team soon discover that the Dodos are host to a deadly parasite, and struggle to stop a pandemic when Tom is infected and - convinced that the government are incubating a mind-controlling biological weapon inside him - goes on the run from the team.

The team investigate the brutal death of a golfer at a golf course, and discover an aerial Anomaly and a Pteranodon in the skies above. Claudia is convinced that the Pteranodon is responsible for the golfer's death and wants deadly force used against it, but Cutter and Stephen are convinced otherwise. Cutter's suspicions are confirmed correct when Claudia is trapped in the golf course's clubhouse by a deadly, flesh-eating swarm of Anurognathus. Meanwhile, Connor accidentally frees Rex from Abby's flat, forcing Abby and Connor to chase Rex across the golf course.

Cutter struggles with the arrival of the ARC's new PR guru, Jenny Lewis, who is physically identical to the lost Claudia Brown, yet is temperamentally a completely different person with no idea of her doppelganger; while Connor gets picked up by a beautiful young woman who is everything he is not, but Abby and Rex are both suspicious of her; and Stephen begins seeing Helen again. When an Anomaly releases a yellow, sulphuric mist inhabited by giant, carnivorous worms on a gleaming new high-rise office block, Cutter and Stephen are sent in to deal with the deadly creatures with Jenny, while back at the ARC, Connor and Abby try and find a fog-battling weapon.

Danny and the team face a Medieval-esque incursion when a Dracorex comes through an Anomaly pursued by a Medieval knight, who - believing he has followed the creature into Hell - causes calamity around modern London as the team try to reason the truth to him. Meanwhile, Connor tries to buy Rex back from Jack's greedy friend.

When the team send a Raptor at an art museum back through the wrong Anomaly, Matt goes through into Victorian London in pursuit of the Raptor, and there he reunites with Emily and attempts to help her escape her grim fate of incarceration at Bedlam Asylum by her shallow husband. Meanwhile, Abby infiltrates Connor's lab to capture Connor's files on New Dawn for Matt.

When a boy's disappearance down a drain coincides with an underwater Anomaly, Stephen and the ARC search the local canal for the aquatic predator behind the disappearance, while Cutter is convinced the creature is somewhere else. Cutter turns out to be right in the worst possible way when Abby is taken by Mer Creatures from the future and held captive in a flooded warehouse cellar. Meanwhile, Cutter and Connor learn that there is a conspiracy within the ARC.

When a young London girl chases her dog through an Anomaly into a harsh, prehistoric desert world, Cutter and Stephen go through on a rescue mission for the girl, but find themselves up against giant sand scorpions. The team's problems only worsen when the Anomaly closes on the trio and leaves them marooned in the hostile desert world.

The team investigate when an Anomaly opens in an Ancient Egyptian artefact at the British Museum, and when a Pristichampsus comes through, Cutter, Abby and Jenny are sent into a race after the giant crocodilian through Central London. Meanwhile, Connor and sparky Egyptologist Sarah Page discover that the Anomaly, the artefact and the creature hold an incredible ancient secret.

Jenny and the team, with unwanted help from Danny, attempt to stop London from becoming engulfed by a pandemic when they face an incursion of a deadly, fast-spreading fungus from the future that turns its hosts into primal monsters. Meanwhile, Sid the Diictodon has escaped Connor's custody into the ARC and is causing calamity, and Jenny learns the truth about Claudia Brown.

Jack searches for answers about Abby's secret life, and gets chased through an Anomaly by a deadly Megopteran; forcing the team to go through on a rescue mission into the desolate, predator-filled ruins of the future.

While the rest of the team deal with a herd of Embolotherium that threaten a rural racing campsite, Danny goes on an infiltration mission to rescue the mysterious Eve from Johnson's forces. But when the team soon discover who Eve really is, her rescue from Johnson has disastrous consequences.

While Connor and Abby try to earn their old positions on the team back, Connor reunites with his old friend Duncan, who leads Connor to a series of homeless killings at a dock area that the team discover are the work of an elusive and deadly Kaprosuchus.

The team investigate an Anomaly incursion at a rural manor house, and reunite with Jenny and discover that the manor is the location for her wedding in the morning; forcing the team to contain a pack of Hyaenodon while ensuring Jenny's soon-to-be-husband doesn't find out. Meanwhile, Jess and Becker are caught in Ethan's deadly trap.

As the team emotionally struggle to recover from the aftermath of Helen's attack, Jenny leads the team to a new Anomaly at an airport; where a Giganotosaurus or "G-Rex" threatens the crew of a Boeing-747, a news crew are attempting to document the incursion for the media, and Danny Quinn gives the reluctant team his unwanted help.

The team learn the truth about New Dawn when Connor creates an artificial Anomaly in the ARC, and trouble soon erupts when the Anomaly unleashes swarming, carnivorous beetles from the future into the ARC, which trigger the lockdown but threaten to burrow out and swarm onto the modern world. The situation is only exacerbated when the beetles trigger Jess' deadly allergy to insect bites, and when Philip threatens to incinerate the entire ARC to stop the beetles.

As Cutter struggles with losing Claudia Brown and with the other consequences of the failed mission into the past and tries to get the team to see that history has been altered, the team are sent to a shopping mall to contain an infestation of deadly, ruthless Raptors. Arguments among the team intensify when Cutter wants all the Raptors tranquilised and sent back through the Anomaly alive.