Scott Lang, under house arrest after siding with Captain America during the events of the "Civil War," grapples with the consequences of his choices as both a superhero and a father. His predicament is compounded when he's visited by Hope van Dyne and Dr. Hank Pym with a new mission. Haunted by a message from the quantum realm, believed to be from Hank’s long-lost wife Janet, they need Scott’s help. With the ability to shrink and grow at incredible speeds, they rely on him despite his legal limitations. Hope dons the suit of the Wasp, showcasing her abilities as they venture to rescue Janet.

Their mission to extract Janet from the mysterious quantum realm is fraught with conflict and danger as they face new adversaries. Ghost, a mysterious figure with phasing abilities due to a quantum accident, seeks the same technology to heal her condition, putting her at odds with Scott and Hope. Meanwhile, the trio also encounters black market dealer Sonny Burch, who is interested in Pym’s technology for his own gain. The team must navigate threats, and Scott’s impending freedom hangs in the balance as they race against time to delve into the quantum realm's uncertainties.