In the bustling chaos of modern-day San Francisco, Scott Lang—a roguish mechanic with a heart of gold—finds himself trapped between two worlds. Once a career thief, he now fights to provide for his daughter, Cassie, while evading the clutches of the law. But his life takes a surreal turn when he stumbles into the hidden legacy of Dr. Hank Pym, a brilliant scientist and patriarch of a fractured superhero lineage.