The team are sent to deal with a Columbian Mammoth rampaging on the M25, and attempt to save a trapped motorist before she frightens the Mammoth into attacking again. Meanwhile, Connor and Abby search for the missing Rex and Caroline, and Stephen reveals his alliance with Helen Cutter. Connor and Cutter spring their trap to find the traitor in the ARC, and Oliver Leek's true colours are exposed and the team race to track him down.

Cutter and the team head to a hospital to deal with an Anomaly and a Diictodon colony wreaking havoc on the hospital's power supply, and also have to help deliver a baby and stop a greedy journalist from getting proof of the creatures. Meanwhile, Helen Cutter and her clone army launch their attack on the ARC, and Helen reveals a secret about the future to Nick.

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.