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!"