Banshee is hunting for Factor Three in Europe. He finds their lair, but is attacked by a robot spider. He escapes and manages to send a message to the X-Men to "beware the spider" before falling unconscious. Factor Three's minions arrive and take him captive.

In Westchester county, Spider-Man has gotten lost but decides to spend the day in the country-side. Just as he's about to relax, a Flying Saucer lands and another Factor Three mechanical spider emerges, hunting for the X-Men. Cerebro registers the robot spider as a mutant and the X-Men rush off to fight it. They arrive just after Spider-Man has dispatched the machine and assume that Banshee's warning was about Spider-Man instead. The X-Men attack the confused Peter Parker who battles them off while professing his innocence. Eventually, the X-Men realize that Spider-Man is telling the truth, and that Cerebro signaled them to this location because the robot was assembled by Factor Three mutants.

Jean Grey had stayed behind to continue searching for Banshee, and manages to find his location in Europe using a crystal that Professor X had embedded in his visor. The X-Men prepare to head to the Swiss Alps to find Banshee and hopefully the missing Professor X.

This is the first team-up of X-Men and Spider-Man.