The movie picks up where the previous installment left off, with Cade Yeager, a struggling inventor, discovering a dormant Optimus Prime in a junkyard. As Cade tries to repair Optimus, he inadvertently awakens the legendary sword Excalibur, which holds the key to the Transformers' existence on Earth. This sets off a quest to uncover the secrets of the Transformers' past and their connection to the mythical sword.