Connor (Andrew Lee Potts) gets kicked off the team for blabbing to his friends about the anomaly.
There have been a couple sightings of giant spiders in the London Underground. An exterminator spraying for rodents is bitten by one of the spiders and eventually dies. At first no one realizes that another anomaly has opened in the tunnels below London. When Claudia (Lucy Brown) finds out about the anomaly she contacts Nick (Douglas Henshall) and the rest of the team. An investigation of the tunnels reveals not only dozens of spiders of all sizes but also a giant centipede. This time the temporal anomaly is from the Carboniferous period.
During the mayhem underground Nick gets separated from Abby (Hannah Spearritt) and Stephen (James Murray). Against orders, Stephen returns to the tunnels to try to find Nick and gets bitten by the centipede. In his feverish state he believes he sees Nick’s wife, Helen (Juliet Aubrey). Unless anti-venom can be found, Stephen will die. Nick has no choice but to return to the tunnels to try to extract some venom from the giant bug. Not knowing what they are up against, the team needs an expert in insects. The only one qualified is Connor.
Episode 2 of season 1 incorporates two prehistoric animals. The Mesothelae was a giant prehistoric spider. They existed over 300 million years ago. The Arthropleura was a giant centipede-like arthropod. It existed around 345 to 290 million years ago. It is believed to have been the largest arthropod ever. Although the creature in Primeval has a poisonous bite, it is believed that the Arthropleura in actuality did not.
A Wilhelm scream can be heard over the radio when the soldiers are being attacked by the spiders, as well as when the exterminator is attacked in an earlier scene.
The outside of the underground scenes were filmed at the Arsenal Station and the Boundary Estate, Bethnal Green. The Underground tunnel was filmed in the Aldwych Underground.