Sent to investigate Charles' death, newly arrived Inspector General Philip allows Lydia to choose a trial by combat in a laser duel to the death with Diana.

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.

Anxious to settle a personal vendetta, Philip trails a Fifth Columnist, hoping he will lead him to the Resistance and Donovan.

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.

The Leader stuns the Visitors by ordering a truce and traveling to Earth to negotiate peace; Diana plots to disrupt the peace.