Note: The Jean in this story and The Dark Phoenix Saga is not the original Jean Grey. After a space mission in which Jean was exposed to radiation after saving the X-men and thereafter died, the original Jean was placed in a cocoon at the bed of Jamaica Bay while the Phoenix, a cosmic entity impressed with Jean’s sacrifice, created a duplicate body of Jean and became known as Phoenix-Jean and unbeknownst to the X-men that it wasn’t their Jean

Immediately precedes the Dark Phoenix saga

A past battle between Magneto and the X-men on Muir Island is what allows Mutant X (Proteus) to escape after being quarantined for 10 years

Jean Grey is at Muir Island with Moira Mactaggert, Multiple Man, Polaris, and Havok

She thought that the X-men died in a battle with Magneto in Antarctica but they are alive and well at X-mansion

Mastermind has begun his illusion casting on Jean’s mind

She is already the Phoenix

Proteus attacks Jean and the X-men fly to Muir Island with Banshee after Polaris tells Cyclops of the attack on Jean

The X-men and Moira Mactaggert search for Proteus in Scotland

Wolverine, Nightcrawler, and Storm encounter Proteus and are easily defeated 

Moira attempts to shoot her son (Proteus) with metal bullets since that is his weakness but misses due to intervention from Cyclops

Cyclops tests the resolve of his X-men by physically fighting them after facing Proteus

Jean Grey telepathically locates Proteus as he continues to take host bodies on his way to kill and use his father as a host

Proteus easily toys with the X-men and gives Moira an ultimatum to accept him or become his new host

A distracted Proteus is shot by Banshee and his father’s host body is weakened giving the X-men an advantage

Wolverine rescues Moira as Proteus is stalled by Havok and Cyclops but slips away and pursues Wolverine 

Proteus takes his mother and prepares to use her as a host but Colossus knocks him away and forces him to be in a pure energy form after the host body is destroyed

Colossus disperses Proteus around the world due to Proteus’s reaction to the metal. X-men think he is dead

Moira desires to clone Proteus (Kevin Mactaggert) for a second chance but Banshee talks her out of it