A group of heroes including Sleepwalker, Darkhawk, Dagger, Araña, X-23, Gravity and Terror (although Araña dies along the way) go to the future to prevent the villain Chronok from stealing Reed Richards' time machine, Chronok having come to the present and already having killed all of Marvel's major heroes.
It's revealed Chronok is from the same time period as Kirkman's Mutant 2099; the group stays with him and his mentor Reed Richards to wait for Chronok. During this time, Sleepwalker experiences difficulties with being away from his host Rick Sheridan, but ultimately comes to terms with it. The team defeats Chronok, but at the end of the story, Richards reveals they can't go back to their present, due to time-travel and alternate timelines. The group decides to stay in the future, satisified with the impact they made, however unnoticed. Mutant 2099 suggests reforming the Avengers or the "Fantastic Nine".