The actor plays Scott Lang, a jailbird-turned-superhero.
Douglas plays inventor Hank Pym, who designs Ant-Man's special suit.
Thanks to Hank Pym's (Douglas) innovation, Ant-Man (Rudd) can shrink himself and control his six-legged namesakes.
When Ant-Man shrinks, he increases his density, thereby increasing his strength.
"I'm Ant-Man," Scott Lang (Rudd) says, revealing his superhero name. "I know. It wasn't my idea."
The actress plays Hope Van Dyne, the estranged daughter of Henry Pym. "The suit has power," she tells Scott Lang (Rudd). "You have to learn how to control it."
"I have been watching you for a while. You're different. And I believe everyone deserves a shot at redemption," Hank Pym (Douglas) tells Scott Lang (Rudd). "Do you?"
Ant-Man (Rudd) must defends the people he cares about after Yellowjacket (Corey Stoll) threatens to "destroy" them all.