Hank, Bobby, Vera and Zelda are taking the subway at midnight when their train is attacked by a monster. After a quick change during the blackout, Beast and Iceman jump out of the train to stop the monster. Even freezing the monster cannot stop its rampage, but Beast and Iceman manage to chase the monster into the tunnels.
Hank and Bobby return to their dates Vera and Zelda. The X-Men are anxious to return to the Institute to report the incident in the subway to Xavier. Thus they have to cut short their date with the girls, disappointing Vera and Zelda.
The monster is still wandering the subway tunnels, trying to remember who he is and how he ended up in the subway tunnels. He was once Prince Gor-tok from a subterreanean warrior race. His father King Kronos led their people to conquer the “outer world”, but they encountered a radioactive blast that killed everyone except Gor-tok. Gor-tok has since sworn vengeance, and goes by the name Grotesk.
Back at the Institute, Cyclops, Angel and Marvel Girl are in a training session with Xavier. Xavier is reprimanding the X-Men for their slow reaction times during the session when Hank and Bobby walk in. The already riled up Xavier calls out Hank and Bobby for entering the Danger Room in their “civilian clothing”. Hank tries to talk to Xavier about the incident in the subway but Xavier just storms off to his study. As he wheels towards the door, Xavier demands the presence of Marvel Girl in his study.
As Marvel Girl approaches Xavier, she asks if her team mates should be let in on their secret experiments. Xavier is putting on an act to distance himself with the rest of the X-Men while the experiements continue.
Meanwhile, Hank relates the subway incident to Cyclops and Angel.
At Archer College in Manhattan, Dr Hunt has created “a machine called a Nuclear Oscillotron” that creates “earth tremors”. The board of trustees are appalled at Hunt’s machine, citing that it might “accidentally start a dreadful chain reaction” that could “tear this planet apart at its very core”. The board suspends the use of Hunt’s Nuclear Osillotron until further discussion, and has it relocated.
Grotesk thinks that the “outer world” still out to destroy him with these earth tremors, and he plans to use “the surface-dweller’s device” against “the earth and its masses”.
After some time, Xavier and Marvel Girl emerge from his study. Xavier wants the X-Men to track down Grotesk. But Marvel Girl shall remain behind with Xavier.
Cyclops, Angel, Beast and Iceman return to the subway tunnels. All their searching only leads them to the empty lair of Grotesk. Angel is unable to contact Xavier, so Cyclops sends Angel and Iceman back to the Institute to report their findings while he and Beast remain to wait for Grotesk to reappear.
Meanwhile, Grotesk has made his way to Dr Hunt’s laboratory. He only finds Hunt’s mousey lab assistant who fainted, and no Nuclear Oscillotron.
When Angel and Iceman return, Marvel Girl informs them that Xavier had gotten their message but left the Institute before they arrived. Angel and Iceman tells Marvel Girl what happened, but Marvel Girl cannot leave her post at the Institute. Angel gets suspicious of Marvel Girl and Xavier’s recent behaviour towards the rest of the X-Men.
Grotesk returns to his lair with the lab assistant as his hostage. As Grotesk questions the lab assistance on the whereabouts of the Nuclear Oscillotron, Cyclops and Beast step in to challenge him.