Needing medicine to treat a deadly diphtheria epidemic, Julie and Kyle recruit a youth gang, one of whom may be a Visitor spy, to help steal the serum.

When Philip and Diana install a high tech computer capable of launching a final victory over Earth, the Resistance's only hope at retaliation is a teenaged computer whiz.

Julie and Donovan sneak aboard the Mother Ship to look for a hidden list naming all the Resistance leaders; Diana schemes to have Lydia's brother slain during a ritual celebration.