The story opens with the X-men training in the Danger Room. Today Scott Summers is practicing the speed at which he can blast bean bags that are being launched at him by the Beast. The other boys are involved with some one-upmanship and roughhousing until Professor X calls them to order. Jean's task is to move a block of wood through a series of obstacles as quickly as possible. Their training is interrupted when Professor X detects the presence of another mutant nearby.
He commands the X-men to change into civilian clothes to seek out this new mutant and bring him back to their headquarters. The boys jostle to be the one to take Jean on the mission. Professor X warns Jean to be careful and she tells him, "Don't worry, sir! Remember how well you have trained us." This leaves Charles conflicted because he is consumed by worry over Jean because he loves her, but know it wouldn't be right to act on his love while he leads the X-men and while he's confined to the wheelchair.
The X-men depart to seek out this new mutant and are led astray a number of times until they arrive at the circus. There Cyclops watches the sideshow performance of a young man known as the Blob. Professor X confirms that the Blob is indeed the mutant they seek. Cyclops goes to talk to Blob but becomes annoyed at how obnoxious the man is. Jean and Warren arrived and the Blob decides to go back with them to the X-men headquarters.
At the headquarters Blob is tested by Professor X. The X-men spar in mock combat with the Blob and eventually Professor X offers Blob membership in the X-men. The Blob refuses and Professor X tells the X-men to capture the Blob so that he can remove the memory of their existance and base from his mind. The Blob is able to escape and return to the circus.
The X-men begin to hunt the Blob down so that he rallies an army of carnies to attack their headquarters. He realizes that he is too dangerous to them with the information he has and that they will come after him. The X-men mansion is attacked by a force of carnies that include giraffes, trapezee artists, gorillas, human cannonballs, cowboys, elephants and gymnasts.
The X-men are initially captured and Blob and his men enter the mansion to find Professor X. With Professor X's mental instructions Jean is able to free the team and the Blob and carnies are captured. Blob and the carnies have all memory of these incidents wiped from their mind.
First appearance of Blob.