The now-teenaged mutant messiah named Hope returns to present day, sparking an X-Men crossover event.
The Second Coming saga serves as the third and final chapter in the "messiah trilogy," which began with Messiah Complex in 2007 and continued with last summer's Messiah War, and centers on the mysterious Hope, the first mutant born since the decimating events of M-Day. [...] Second Coming begins with a one-shot and continues through UNCANNY X-MEN, X-FORCE, X-MEN: LEGACY and NEW MUTANTS on a chapter-by-chapter basis before wrapping in a special finale.
[...] The events of "Second Coming" will make it extremely difficult to hide the true nature of X-Force from their fellow mutant comrades. "Secrets can't trump the importance of saving lives, especially since everything as far as Cyclops is concerned hinges on Hope and what she means for the future of mutantkind," Kyle remarked. "So I think that's an issue that will absolutely be dealt with when it comes to the final chapter of this saga."
Each chapter of the story flows into the next one, and each writer will be playing with their normal cast of characters as well as ones who don't usually appear in their book. [...] You'll see characters from all over appearing all over the place.
Sources: Marvel.com, CBR