Last issue, Professor X was kidnapped. Instead of doing anything about it, this issue involves the kidnapping of Cobalt Man by Tyrannus.
When they go underground to Tyrannus’ kingdom, they instead find Mole Man, who is able to expose the mutants to the Mists of the River Lethe, which turn them into his slaves.
Meanwhile, Tyrannus weaponizes Cobalt Man and sends him to attack Mole Man. Mole Man’s X-Men defeat him, and then Cyclops and Beast (who were not part of the team hypnotized by Mole Man) come in and save their pals.
Chaotic and stupid. They should have been looking for X, not getting involved in this underground war.