After receiving Magneto's invitation, the Sub-Mariner comes to his hidden isle to consider joining the Brotherhood against the humans on the surface world. Concerned that the Sub-Mariner will join the evil mutants, the X-Men go to the isle to prevent this, hoping that he will join them instead. The X-Men end up fighting the Sub-Mariner also while fighting against the Brotherhood after their ship is destroyed by Magneto's giant magnet. (Cover Date: July, 1964)

[Iceman weirdly has the ability to make ice cream in this story.]