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.