A British submarine collides with a Liopleurodon in the North Sea as an anomaly opens up. Jess (Ruth Kearney) contacts the team. They meet Captain Marcus Yates (Tom Sullivan) at the docks. Since this is a top-secret mission, the captain only has a skeleton crew on board. The plan is to have the submarine return to the anomaly. Matt (Ciaran McMenamin) and Connor (Andrew Lee Potts) have rigged an anomaly closing device inside a torpedo. They will then launch the torpedo at the anomaly to close is.
When the ship surfaced after being hit, they found a marine animal caught up on the bridge. They brought it aboard believing it was dead. When Abby (Hannah Spearritt) checks the animal, she realizes it is a Swimming Theropod from the Jurassic period. It is also still alive, but in shock. Abby has the animal put in the ship’s freezer to contain it.
As they draw closer to the anomaly, they are again attacked by the Liopleurodon. The damage created by the animal causes the sub to lose power and injures the captain. With the captain out of commission the next highest-ranking officer is Midshipman Sam Leonard (Allen Leech). Without power, the lock to the ship’s freezer opens and the Theropod is free. In addition, the submarine gets sucked through the anomaly and into the Jurassic period.
At ARC, James (Ben Miller) receives a visit from a pompous Admiral Marston (Bosco Hogan). Marston suggests that they blow up the anomaly. James assures the admiral that their form of containment will be sufficient. When the submarine disappears into the anomaly, Admiral Marston takes over command of the situation and orders that the anomaly be nuked.
Matt finds out what happen to Emily (Ruth Bradley) after she returned to the 19th century.
Episode 2 of season 5 features a Liopleurodon and a swimming Theropod. Liopleurodon was a species of large marine reptile, specifically pliosaur, from the Jurassic period. The name means “smooth sided teeth”. The Swimming Theropod was a semi-aquatic, dromaeosaur-like species of theropod from the Jurassic period. The specific type of theropod is not mentioned.