Previously, Beast and Jubilee subdue a rampaging Sabretooth and brings him to the Institute. Unbeknownst to them, Sabretooth is assimilated by a being known as the Phalanx, which consumes matter. Mr Sinister tries to contact Professor Xavier to warn him of the Phalanx but Xavier is captured by the Phalanx, as well as the rest of the X-Men. Beast manages to escape, with the help of a rebel Warlock Phalanx named Self. In an attempt to escape the Phalanx colony Self and his lifemate crash lands on Earth. The Phalanx colony tracks them to earth and intends to add earth to the Phalanx empire.
Beast and Self meet up with Forge and Quicksilver (who is later captured). An unlikely ally, Sinister helps Beast, Self and Forge escape to Muir Island, where Beast succeeds in creating a virus to destroy the Phalanx. An unlikely alliance is forged between Beast, Self, Forge Sinister, Amelia Voght and Magneto. They learn that Cameron Hodge, an enemy of the X-Men, is collaborating with the Phalanx to assimilate all life on earth, including mutants. They test the virus on a Phalanx assimilated sample, which reverted the matter to its original state.
The alliance heads for the Empire State Building, headquarters of the Phalanx. Forge, Sinister and Amelia and starts to free the X-Men. Meanwhile, Beast, Magneto and Self prepare to feed the virus to the Phalanx core. Peace and order is restored, as is Self’s lifemate.