Challengers de l'inconnu [Ace Morgan; Prof Haley; Red Ryan; Rocky Davis]; June Robbins (introduction); Felix Hesse (introduction); ULTIVAC (introduction)
Felix Hesse, a German scientist, comes pleading to the Challengers to save him from Ultivac, "a creature of my own making... but now out of control!" He explains. Interned as a war criminal, he met Floyd Barker, a bank robber. Released, they team to build a giant machine - Suddenly a giant robot hand crashes through the window and seizes Hesse. Spouting propellers, it flies off with Hesse. The Challengers have their next job, "Track down ULTIVAC!"