After an epic battle, a great city lies in ruins, but the Earth itself is saved. As humanity begins to pick up the pieces, a shadowy group emerges to try to take control of history. Meanwhile, an ancient and powerful new menace sets its sights on Earth. A new group of humans, led by Cade Yeager (Mark Wahlberg), helps Optimus Prime (Peter Cullen) and the Autobots rise up to meet their most fearsome challenge yet: a worldwide war of good versus evil. Optimus Prime (Peter Cullen) believes that resurrecting ancient Transformer Sentinel Prime (Leonard Nimoy), once the leader of the Autobots, may lead to victory. That decision, however, has devastating consequences; the war appears to tip in favor of the Decepticons, leading to a climactic battle in Chicago.