Ant-Man and the Wasp

Concurrent with Infinity War, and tonally oblivious to it, which is the joke. Hank Pym and Hope rescue Janet van Dyne from the Quantum Realm after thirty years.

In the mid-credits scene, Scott goes into the Quantum Realm to collect healing particles for Ghost, with Hank, Janet, and Hope operating the tunnel from a van on the surface. The Snap kills all three mid-operation, leaving nobody to pull him out. He's stranded — five hours subjectively, five years externally. That stranding is the mechanism for the next film.

Ghost is Ava Starr, this film's antagonist: a quantum accident killed her parents and left her permanently phasing between states of matter, in constant pain. She was raised and weaponised by S.H.I.E.L.D. She's stabilised, not cured — and she ends up on the Thunderbolts roster.

Hank and Scott are never Ant-Man simultaneously. Hank was the original in the 1980s, retired, and handed the suit to Scott in 2015. Hope takes her mother's identity as the Wasp. Hank stays out of the suit entirely.