It seems that an alternate time line has been created in which Xavier doesn't exist. All the mutants unite as one to fend off the humans machinery, but Bishop and Shard see to it that the assassination is stopped. The Storm and Wolverine of the alternate time line tag along, and immediately find Xavier. They encounter Nimrod and Fitzroy, but it seems that Fitzroy already plotted Xavier's dead by planting a bomb in his room.
This episode is automatically awesome because of the first seven minutes. War movies are my favourites, especially sci fi ones. Seeing all the mutants, especially an aging Magneto and Sinister, fighting on one side with the other X-Men, excites you in a way. Even the Avengers making a cameo appearance was cool.
What I also like is how all of these stories are connected with one another, but only through a minor concept. Such as Bishop, which tells of the events directly before the Beyond Good and Evil arc. Though the thing I like the most is how X-Men so far handles time traveling. Everything is structured so well, and it's all very cleverly plotted. Also, me being a huge Mastermold fan, it's a treat to finally see him make an appearance. His tyrannical attitude towards Fitsroy was also pleasing to see.