Ant-Man and the Wasp: QuantumaniaSave

Post-Endgame Los Angeles. Scott Lang (Paul Rudd, in a tailored suit) has been a celebrated public figure since the Snap reversal. He has authored a memoir titled "Look Out For The Little Guy" — a self-aggrandizing account of his role in saving the universe via the Quantum Realm in Endgame (2019). He's on a national book tour. He attends premieres. He gets approached on the street for autographs. His Avengers fame has eclipsed every reasonable level of celebrity. He's been ignoring his teenage daughter Cassie Lang (Kathryn Newton, replacing Abby Ryder Fortson and Emma Fuhrmann as the older Cassie from her earlier films), who is now 18 and has been quietly building her own scientific identity.

Cassie. Cassie has been a Quantum-Realm activist for years — using her Pym Particle access to help blip-displaced families locate missing relatives. She has secretly built a small Quantum-Realm signal-transmitter device in her basement workshop. She has been transmitting signals into the Quantum Realm hoping for a response. She hasn't told her father about it.

The pull. At a family dinner at the Pym residence, Cassie demonstrates her transmitter to Hank, Janet, Scott, and Hope. Janet — who has spent 31 years stranded in the Quantum Realm — recognizes the device's signal pattern and is horrified. She tries to shut it down. She's too late. The signal has already pinged something deep in the Quantum Realm. A massive interdimensional force pulls the entire Pym family — Scott, Hope, Cassie, Hank, Janet — through the device's signal-aperture and into the Quantum Realm. They fall into a subatomic blue-and-green ecosystem of alien geometry.

Janet's hidden history. Once in the Quantum Realm, the family separates — Janet, Cassie, and Hank land in one Quantum-Realm city; Scott and Hope land in another. Janet, who has been hiding a secret from her family for thirty years, finally confesses. While she was lost in the Quantum Realm from 1987 to 2018, she met a man — a humanoid being trapped in the same realm — who claimed to be a refugee from a future cosmic civilization. She and the man had worked together for years to build a Pym-Particle-powered escape engine. She had then discovered, mid-construction, that the man was in fact Kang the Conqueror — a multiversal-warlord variant who had been exiled to the Quantum Realm by his own future selves. Janet had sabotaged the engine, leaving Kang permanently stranded. Kang has been hunting her ever since.

Quantum Realm civilizations. The Quantum Realm is revealed to be a fully-populated dimensional ecosystem — multiple intelligent civilizations have developed over millions of years across its alien geographies. There are pirate ports, refugee settlements, futuristic city-states, and a brutal totalitarian regime currently ruled by Kang. Scott and Hope land at a junker outpost called Krylar's Tavern, owned by a humanoid figure named Lord Krylar (Bill Murray, in a single-scene cameo as a former love interest of Janet's). Krylar reveals that Kang's army has been hunting Quantum-Realm rebels for years. Scott and Hope head toward the rebel base in the Veridian Forest.

The Veridian rebels. Hank, Janet, and Cassie find their way to the rebels' hidden encampment. The rebellion is led by Jentorra (Katy O'Brian), a green-skinned Quantum-Realm warrior whose people were genocided by Kang's conquest. The rebellion includes humanoid, plant-form, blob-form, and crystalline-life-form citizens. The Pyms join the rebels. They begin planning resistance operations against Kang's Probability Storm — a Pym-Particle-powered weapon that allows Kang to escape the Quantum Realm and conquer the broader multiverse.

Kang's confrontation. Scott and Hope are captured by Kang's army. Cassie is captured separately at the rebel base. Scott meets Kang face-to-face in the Throne Chamber. Kang — Jonathan Majors, regal and weary in flowing purple-and-blue armor — has been waiting for Janet for thirty years. He demands Scott steal a specific Pym Particle core from inside his floating power-station — the Multiversal Engine, which can teleport Kang's ship out of the Quantum Realm into the multiverse proper. Kang demonstrates his power: he can rewind time within local space-time bubbles. He can rewrite people's deaths. He can disintegrate matter at a glance. Scott agrees to steal the core if Kang spares Cassie's life. Kang accepts. He warps Cassie to a holding cell.

MODOK. Inside Kang's lower-tier guard force is a horrifying creature — a floating disembodied human head with two atrophied limbs hanging beneath a metallic flotation device. It's M.O.D.O.K. — Mental Organism Designed Only for Killing — and the human face is Darren Cross (Corey Stoll, reprising his Yellowjacket role from Ant-Man). Cross had not died at the end of Ant-Man as everyone assumed. He had survived the Yellowjacket explosion and been trapped in the Quantum Realm. Kang had recruited him and rebuilt his shattered body into a giant flying disembodied head. Cross has been MODOK for eight years and is now Kang's mid-tier enforcer.

Probability Storm. Scott and Hope infiltrate Kang's flagship power-station to steal the multiversal engine core. The interior is a Probability Storm chamber — a quantum-uncertain volume of space where physical possibility manifests as visible variation. Scott walks into the Probability Storm and his body fragments into thousands of slightly-different versions of himself across overlapping waveforms. Each variant Scott Lang has a slightly different memory, slightly different costume, slightly different attitude. They argue with each other. They climb over each other to reach the core. Scott eventually pulls himself together (literally — the variants merge back into one Scott) and extracts the multiversal engine core. He hands it to Hope. They escape the chamber.

Cassie's transformation. Cassie has been imprisoned in a holding cell with the captured Jentorra. Cassie has been smuggling small mechanical components and Pym-Particle reserves throughout the film. She breaks out of the cell, takes Jentorra's armor as a base, and assembles her own Pym-Particle-enhanced superhero costume. She becomes Stinger — a costumed superhero of her own, capable of size-shifting and energy-blast attacks. She rallies the rebels into a coordinated assault on Kang's throne.

MODOK's redemption. Cassie, in her new Stinger costume, encounters MODOK during the rebel assault. She has a quiet conversation with him. She tells him she remembers him from her childhood — Cross had been kind to her when she was little (in Ant-Man). She knows there's still a man inside the floating head. She offers him a chance to defect. Cross, after a long pause, agrees. MODOK turns against Kang. He uses his floating disembodied form to hold Kang in place during the final battle, sacrificing himself in the explosion. The death-redemption-arc of Cross/MODOK is the film's most-meme'd moment.

Kang's defeat. Scott and Hope, in their Ant-Man and Wasp suits, fight Kang directly in the power-core chamber. Kang is overwhelmingly powerful — he has multiple cosmic-energy weapons, body-armor, and time-manipulation skills. The fight goes badly for Ant-Man and the Wasp for ten straight minutes. Then Scott does the unexpected. He summons the Ant Army — every ant Scott has ever bonded with telepathically, plus dozens of Quantum-Realm-trained super-ants Hank had introduced into the Realm decades ago — and the swarm overwhelms Kang's defensive systems. Scott and Hope shrink to subatomic size, get inside Kang's armor, and force him into the power-core's reactor itself. Kang is sucked into the core. The core detonates with him inside. Kang is gone — for this variant.

Aftermath. Cassie's transmitter signal — the one that had triggered the whole Quantum Realm trip in the first place — is now strong enough to open a return portal home. The Pym family escapes back to Earth. Scott, Hope, Cassie, Hank, and Janet emerge in the Pym residence's basement. The kitchen clock has not even ticked forward — the entire Quantum Realm adventure took several weeks for them subjective-time but only minutes in Earth-time. Scott pulls Cassie into a hug. He acknowledges her independence. They reconcile.

Scott's doubt. Days later, Scott is walking through downtown Los Angeles and stops at a crosswalk. He suddenly remembers something Kang said to him in the Quantum Realm. Kang had warned: "You think you've defeated me. You've just stopped one variant. There are millions of us. We're coming." Scott had not taken Kang's warning seriously. He still doesn't. He shakes off the memory and continues walking. The audience, however, recognizes the threat is real. Cut to the multiversal council scene.

Mid-credits. A vast amphitheater-shaped meeting chamber outside time and space. Thousands of identical figures wearing identical Kang-style purple armor sit in concentric rings. They are all variants of Kang the Conqueror across the multiverse. At the center podium is a tall, gold-armored variant — Immortus, the eldest of the Kang variants. He addresses the assembled council. "He failed us. The Conqueror who was trapped in the Quantum Realm has been killed by a small-time hero named Scott Lang. The multiversal Council has been jeopardized. We must accelerate. Every Kang variant in every reality. We have a war to wage." Three more identifiable Kang variants step forward — Rama-Tut (in Egyptian regalia), Centurion (in armored breastplate), and Pharaoh (the bearded historian variant). The Kang Dynasty is being assembled. Cut to credits.

Post-credits. The Time Variance Authority headquarters from Loki (2021). Loki (Tom Hiddleston) and Mobius (Owen Wilson) are at a Chicago World's Fair sideshow in 1893. They've been tracking down a particular Kang variant — Victor Timely — who has been operating a small mechanical-clock-and-electrical-circuit booth at the Fair, advertisizing his services as an inventor. Loki realizes Timely is a Kang variant they need to capture before he becomes Immortus. The post-credits scene directly leads into Loki Season 2 (2023). Cut to credits.