Mike is an unmotivated stoner whose small-town life with his live-in girlfriend, Phoebe, is suddenly turned upside down. Unbeknownst to him, Mike is actually a highly trained, lethal sleeper agent. In the blink of an eye, as his secret past comes back to haunt him, Mike is thrust into the middle of a deadly government operation and is forced to summon his inner action-hero in order to survive.

Armed with the astonishing ability to shrink in scale but increase in strength, master thief Scott Lang must embrace his inner-hero and help his mentor, Doctor Hank Pym, protect the secret behind his spectacular Ant-Man suit from a new generation of towering threats. Against seemingly insurmountable obstacles, Pym and Lang must plan and pull off a heist that will save the world.