Written by Chris Claremont with art by John Byrne and Terry Austin, this issue concludes the two-part "Days of Future Past" story started in 141. This is the first actual issue of Uncanny X-Men. Issues 1-141 are officially X-Men (1st series). This issue has been reprinted in Classic X-Men, an Essential X-Men trade paperback, and in several editions of X-Men: Days of Future Past.
In the future, Katherine Pryde plays a desperate gamble to save mutantkind from near-extinction. Projecting her mind across time into her teenage body in the past, Pryde convinces the X-Men to save the life of anti-mutant Senator Robert Kelly from the reformed Brotherhood of Evil Mutants. The villains attack and initially seem to have the upper hand, as the X-Men are being led by the still untried Storm in the wake of Cyclops' departure. Professor Xavier and Moira McTaggert are hurried away by a policeman, who is actually Mystique in disguise. She subdues them and uses them as hostages. Kate/Kitty Pryde/Sprite decides to remain close to Senator Kelly in case any of the Brotherhood manages to elude her teammates. The United States Army attempts to prevent the Brotherhood from advancing, but are thwarted by the Blob and Avalanche. Colossus works to help the military, while Wolverine is burned by Pyro’s flame creature. He is saved by Storm. The Canadian mutant then finds himself confronted by two Nightcrawlers. He decides to use his claws to find out which one is his teammate, gambling that the doppelganger has only copied Kurt Wagner's appearance, and not his powers. Storm forbids him from using his claws in non-lethal situations. The heroes manage to beat their foes, and the second Nightcrawler is revealed as Mystique, astonishing the true Nightcrawler with their physical similarities and the fact that she knows, not just his true name, but that of his foster mother. Mystique escapes and the X-Men realize that both Sprite and Destiny are unaccounted for. Destiny intends to kill Senator Kelly with a crossbow but Sprite manages to throw off her aim at the last moment before she gets exchanged with Kitty again. Before leaving with Sprite, Storm asks Kelly to consider that his life was saved by mutants even at it was threatened by others, and to reevaluate his stance on mutants. Later, the X-Men wonder if they’ve managed to change that future Kate came from. One month after the battle, the unidentified President of the United States meets with Kelly, Henry Peter Gyrich and Sebastian Shaw in private. Based on Kelly’s recommendation, the president advocates for Project: Wideawake, to be led by Gyrich, a program that includes the use of Sentinels to deal with the perceived mutant menace.
Meanwhile, Katherine Pryde's teammates in the future infiltrate a Sentinel base in order to prevent the malevolent robots from spreading their influence across the globe. One by one, though, the X-Men are slain. Will their gambit pay or will the Sentinels emerge victorious?
This story has had far-reaching consequences within the X-Universe, and is the basis for the 2014 X-Men: Days of Future Past film. In the film, though, Katherine Pryde facilitates the transference from past to presence by placing the subject's mind "out of phase," and it is Wolverine who travels back because his healing factor makes him more likely to survive any anticipated physical trauma from the process. Also, it is Bolivar Trask (played by Peter Dinklage) who the heroes are attempting to save from Mystique.