X-Men #27 continues the plot thread from the previous story, with Jean Grey's having met new co-student, Calvin Rankin (AKA Mimic), who is sure he's seen Jean before. It starts with a four page flash-forward of a powered Mimic defeating the X-Men (minus Warren), and then goes back to the end of the last issue, taking a full nine pages to bring the story to Mimic's attack.
Mimic is being manipulated by the Pupper Master, in some sort of scheme to get revenge on the Fantastic Four. There are small cameos from Quicksilver and the Scarlet Witch and Spider-Man, who all decline to team up with the X-Men. And then we are told that the apparent defeat at the start of the issue was a fake-out on Xavier's part. Structurally this is surprisingly sophisticated stuff.
Jean is still at college, although she gets involved in fighting in the issue. She here completes the hat trick - having previously been the only X-Man to have cooked, and having acted as nurse, she's now made new costumes for the team. O-kay!