After Captain America’s frozen body is discovered in the Arctic, Arnim Zola unleashes Doughboy on New York City to distract the Avengers while Baron Zemo battles Captain America.

Captain America ponders the mystery of the Winter Soldier and enlists Nick Fury’s aid to find him when the Red Skull escapes from prison and massive robots – the Sleepers – arise as part of a contingency plan by the founder of HYDRA to destroy Washington, D.C.

The Leader has placed an expanding dome of pure gamma radiation around the Cube, with anyone caught inside it being mutated into a Gamma Monster. The Avengers, along with the support of S.H.I.E.L.D., enter the Cube in an attempt to the destroy the Gamma Generator.

Hulk tries not to get captured by S.H.I.E.L.D. and Hulkbuster units, while Hawkeye is betrayed by Black Widow who is apparently working for HYDRA.