The X-Men continue their training. In this story, they must deal with The Blob, a mutant who can't be moved unless he wants to be. Professor X believes the Blob will join them, but the mutant isn't interested, and he knows the secret of the X-Men. Both he and they realize how dangerous that makes him, setting up a fight. The back story concludes how Scott (Cyclops) first met Professor X, and how Jack O'Diamonds met his apparent end, blasted to bits when his diamond hard form because too rigid to function.