After relentless persecution and a near fatal Sentinel attack, the Uncanny X-Men and their mutant revolution are going on the offensive, their target? The international spy organization S.H.I.E.L.D.! But as Cyclops' team fights to save their species, are they only digging themselves into a deeper hole? Who is the mysterious figure building S.H.I.E.L.D.'s Sentinels? Is S.H.I.E.L.D. really responsible for the attacks? Charles Xavier's last will and testament will be discovered, what's concealed within its pages might be the X-Men's undoing!