This issue has a reprint from X-MEN #9 , wherein the X-Men are summoned to Europe by Professor X, who is hunting down the villain Lucifer, the man who cost him the use of his legs in some hinted-at story that wouldn’t be told until after Kirby stopped drawing the book. The Avengers also wind up in the same region, apparently thanks to Thor’s hammer detecting evil rays or something. Yeah, I don’t know what that’s all about, but it was the Mighty Marvel Age of crossovers.
The Professor finds Lucifer, but finds out that he’s rigged a bomb to explode if his heartbeat stops, so he mentally orders the X-Men to stop the Avengers from interfering. So of course, they fight…
There’s a classic Marvel panel of the era, ten heroes, each with some dialogue or thought balloons.
Eventually Professor X communicates with Thor and convinces him that they should let the X-Men handle this, and the team re-joines the Professor to defuse the bomb. And for some reason the Professor then lets Lucifer go now that he knows he can be defeated. So much for Xavier’s vow earlier to make sure he never menace humanity again.
The fight with the Avengers is a bit formulaic, and the end a bit abrupt, but otherwise a solid story with a few funny scenes (like the American tourist who runs in the Avengers and the X-Men).
Chic Stone inks the 20-page story, and the original Kirby/Stone cover is also reprinted as a pin-up in the back of the book.