Rory MacNeil, a rugged old Scotsman, reluctantly leaves his beloved isolated Hebridean island and travels to San Francisco to seek medical treatment. Moving in with his estranged son, Rory sees his life transformed through a newly found bond with his baby grandson.

Just when his time under house arrest is about to end, Scott Lang once again puts his freedom at risk to help Hope van Dyne and Dr. Hank Pym dive into the quantum realm and try to accomplish, against time and any chance of success, a very dangerous rescue mission.