Classic X-Men / X-Men Classic #9

Plot

The X-Men's shuttle crash lands in Jamaica Bay and Jean rises from the wreckage as the Phoenix; To facilitate Jean's recovery, Prof X sends all of the X-Men but Cyclops to Scotland on vacation where Banshee has just inherited his ancestral castle; The X-Men show up at the castle and find it already inhabited by Sean's cousin Tom and his pal Juggy. Of course, as all now know, Jean and Phoenix are two separate entities (the latter taking the former for a template), and not the same being as the story insinuates.