Their task isn't helped by dogged journalist, Mick Harper, who is determined to catch one of the creatures and expose the ARC and its secrets to the world.
By the end of the episode Connor finds that he has adopted two adorable new pets to join Rex in his menagerie.
Meanwhile Lester, Jenny and Sarah are confronted with an attack on the ARC, led by Helen and a small army of 'Cleaner Replicas'. The rest of the team arrives in the nick of time and a battle plays out throughout the ARC. Will Helen finally win?