With many of the original party returned to their own time, Varian, Scott and Fred find themselves caught up in the machinations of a being called The Source, which has enslaved the inhabitants of the city of Atlantium, built by the survivors of the original Atlantis. The Source plans to us Scott's life force to regenerate itself. The trio are aided by Liana, who reveals that she is half alien.

• Richard Fielder
• Leonard Katzman
• Bruce Lansbury

• Richard Jaeckel
• Richard Lawson
• Ian McShane