This is the whole plot I found online
Movie opens with a flashback to Hank and Janet going on a 'business trip' and saying goodbye to Hope. Flashback is then an expansion from the first film where Janet shrinks to sub-atomic level to disarm a missile (only this time with dialogue and scenes of Janet entering the quantum realm). It then cuts to Hank and Hope after the end of the first film, where Pym reveals that Scott's trip to the quantum realm has reignited his hope that Janet is still alive, and Pym shows Hope old blueprints for a machine that might be used to save Janet.
Two years after Civil War Cassie is visiting Scott for the weekend at Scott and Luis's apartment. Scott and Luis are starting a new security business with Dave and Kurt called X-Con. Cassie and Scott are playing around when Scott's leg crashes through the fence, outside the perimeter of his house arrest. The FBI and Jimmy Woo show up and remind Scott that his house arrest ends in a few days and check that he has not been in any contact with Hank or Hope (who are wanted after the Soviet Accords and their connection to Antman and the suit). Scott assures Woo that he hasn't been in contact and that Pym would likely not want to hear from him anyway.
Scott takes a bath and falls asleep in the bath where he has a vision of Janet. The dream changes to what appears to be a memory of Janet playing hide-and-seek with a young Hope, with Scott viewing the memory from Janet's perspective. He wakes up. Scott pulls a hidden cell-phone out of the wall and calls Pym and leaves a message about the dream. Scott goes to eat cereal but is then tranquilized by a flying ant. He wakes up in a car next to Hope. He is immediately alarmed to be outside of the house, but Hope reassures him that the ankle detector was left on an enlarged ant, who is mimicking Scott's routine inside the house.
She drives Scott to an abandoned building that actually has an advanced lab inside. Hope and Pym explain that they've been building a big portal that they believe will give them access to the Quantum Realm so they can retrieve Janet. They actually tried turning it on last night, but it shut down after only a few moments. Scott called them about the dreams minutes later. Hope and Pym believe Scott's experience in the Quantum Realm gave him some kind of mental link to Janet, and need him to help bring her back.
Scott is insistent that he return home in time to get the ankle sensor removed, but Hope reassures him that they will be able to return him by then.
Scott, Hope, and Pym go outside to shrink the entire building into a portable box and leave in a van. Pym asks about Scott's suit, making sure that Scott destroyed it and did not allow it to fall into the wrong hands. Scott confirms he destroyed it. The three of them drive to a restaurant owned by Sonny Burch, a black market dealer. Hope goes alone to do the exchange under an alias while Hank and Scott watch through a monitor. Burch reveals to Hope that his contact in the FBI has told him Hope's true identity. He refuses to sell the technology part and attempts to blackmail Hope into having Pym create technology for him that he can sell. She refuses and pretends to leave.
Hope actually changes into the Wasp costume and gets the tech part. She almost succeeds when Ghost suddenly appears, who attempts to take the tech part for herself. Pym gives Scott a new suit to help Hope, but he warns Scott that the suit isn't completely finished. Scott and Hope fight Ghost for a bit, but then she escapes with the tech part as well as the mini building.
Pym, Hope, and Scott decide to go to Bill Foster to find a way to track the lab.
They go (in disguise) to the university where Foster is a lecturer and Foster immediately recognizes Pym. Foster reveals he used to work with Pym on Project Goliath. He claims he was Pym's partner, but Pym objects to this. Foster claims he left because he was sick of dealing with Pym, but Pym claims he fired him. They see the FBI out the window, clearly looking for them. The three get away, and Foster tells Woo and the FBI that he hasn't seen Pym in years. Foster ultimately wasn't any help finding the lab. Pym mentions that if he had access to his older tech, he could track the lab with it.
Scott reveals he did not destroy his original suit, instead shrinking it and hiding it away. Scott hid the old suit within a World's Greatest Grandma trophy given to him by Cassie, but she has taken it to school with her for Show and Tell. Hope and Scott infiltrate the school and retrieve the trophy (Scott's new suit malfunctions making him the size of a child, which he uses to blend in).
Pym tracks down the lab to a building where Ghost has set up a chamber that she appears to use to regulate her phase-shifting. Hope and Scott attempt to steal the lab back, but Ghost awakens and takes them out. Scott wakes up with Hope and Pym tied up next to him. Ghost claims to not want to hurt Scott, but wants to use his connection to Janet. Foster reveals himself to be working with Ghost.
We get more flashbacks discussing how Ghost's father (who I believe is Elihas Starr AKA Egghead) had also worked with Pym, but had been fired and discredited by him. An explosion occurs which kills Ghost parents and gives Ghost her powers. A young Ghost is comforted by Bill Foster who gives her a teddy bear. Ghost came to work for SHIELD, who created her suit to help control her abilities. They used her as a spy and assassin. After SHIELD ended, Foster took care of her and built her the stability chamber.
Ghost believes Pym's portal is the key to curing her, as the phasing is incredibly painful to her and will eventually kill her. Her plan is to draw quantum energy from Janet which could kill her (Janet). The tri manage to escape with the help of some ants take the mini lab and tech parts with them.
Now that they have the lab back and all the parts of the portal, Pym and Hope attempt to activate it again. Nothing seems to happen, with Scott unable to sense Janet. Suddenly, Scott walks over to the computers and starts editing data. Pym and Hope attempt to stop him, but it turns out to actually be Janet temporarily possessing Scott's Body. Scott lovingly caresses Hank's face as Hank and Janet (through Scott) are reunited. Janet gives Pym and Hope coordinates to her location within the Quantum Realm. She tells him they will have to act quickly, and only have once chance. The portal closes back up, with Scott having no memory of what just occurred.
Meanwhile, Foster reveals to Ghost that the chamber is no longer effective, and that she may only have a matter of days or weeks to live.
Luis calls Scott and Scott gives Luis the lab's current location, which is deep in the forest. As Luis is leaving, he is stopped by Burch and his people who want to know how to find Scott. Burch has his goons tie up Luis, Dave, and Kurt. One goon uses truth serum on Luis. When asked where Scott is, Luis starts telling a story in the same style as the first film, talking about how he met Scott, Scott's relationship with Hope, and where Scott is emotionally.
Burch asks where Scott is literally. Luis tells him.
Ghost, who was invisible and eavesdropping departs for the lab. Burch reasons that it will next to impossible to get Pym's tech from Ghost. He calls his FBI contact, who turns out to be one of Woo's men, telling him Pym and Scott's location. Luis calls Scott to warn him that Ghost and the FBI are on their way. Scott warns Pym and Hope to hurry. He has to leave them now in order to get back home before the FBI find him missing.
Pym and Hope shrink the lab in an attempt to relocate, but the FBI are already there. The lab is confiscated and Pym and Hope are arrested. Thanks to Cassie stalling Woo, Scott is able to return home on time. Woo and Scott receive word that Pym and Hope are in custody. Burch's FBI contact attempts to sneak away the lab, but Ghost takes it from him. Pym and Hope, in a police interrogation room, free themselves from their handcuffs and formulate a plan to blow up one of the walls to escape. Scott stops them by dropping in Hope's Wasp suit and a FBI disguise for Pym, covering the security camera with ants (similar to what Hank did in the first movie). They escape together. Pym had created a new way to track the lab, so they are able to immediately locate it again. Ghost has moved the lab to another part of the city with Foster.
Scott draws Ghost out to an adjacent building. Pym retakes the lab from Foster with giant ants, intending to make the trip to the Quantum Realm himself. Pym tells Foster that he fully intends to help Ghost after he's saved Janet. Foster wishes him good luck. Pym goes through the portal. Foster is escorted outside the building by the ants. Hope then re-shrinks the building. The plan is to regrow the building in time for Hank and Janet to return through the portal. There's a big car chase sequence, with the building and the remote to shrink/grow the building repeatedly changing hands between Ghost, Scott, Hope and Burch.
Meanwhile, Pym flies into the Quantum Realm in his little ship. He eventually steps outside of it to look for Janet. It seems he cannot find her, and Pym starts hallucinating. Janet comes to save him. She places her fingers on his temples and is somehow able to remove the disorientation that the Quantum Realm induces. She claims to have changed in a way she can't completely explain. She and Pym kiss.
Ultimately, Ghost is left behind during the car chase, and Burch runs on foot with the shrunken building to the Fisherman's Wharf. He boards a whale-watching boat, Scott going after him. Scott grows to enormous size and simply swims up to the boat (at one point being mistaken for a whale) and takes the lab from Burch's hands. Scott places the building down by the pier, clearing people away from it. He passes out from the strain of growing so large, and Hope dives into the sea to save him. She brings him back to land, Scott wakes up, and they kiss.
Ghost takes the remote from Luis and grows the building. Foster runs in after her. Foster attempts to talk her out of her plans out of concern for Janet. He reasons that Janet is also a brilliant scientist and may be able to help upon her return. Ghost refuses, saying it's easy for Foster to try to pick the high road when he's not the one dying. She tosses him aside and turns the portal on, which has been hooked up to her stability chamber. In the Quantum Realm, Janet begins to phase away. Scott and Hope arrive, stopping the process. They and Ghost fight. Pym and Janet's vessel arrive through the portal, they hit Ghost but Scott and Hope are able to move out of the way.
Hope and Janet have a tearful reunion. Ghost gets back up but Janet touches her fingers to Ghost's temples and appears to use her new abilities to cure Ghost of her affliction. Luis arrives to warn them that the FBI are on their way. Scott blows up his suit and uses it to distract Woo and the FBI while everyone else can make their escape. Ghost and Foster run off on their own. Ghost implores Foster to leave her but Foster swears to never abandon her, and they hug. Scott is again able to arrive home before Woo. The FBI have no choice but to remove his ankle sensor as his house arrest has ended.
During the commotion, Dave and Kurt apprehended Burch and his goons, using the truth serum to make them admit their crimes to the police. They end up on TV for their heroism, and X-Con gets an increase in clients. Later, Scott, Cassie, and Hope watch a drive-in movie together (Actually a shrunken car watching a laptop screen) and Hank and Janet grow a house on the beachside.
In the post-credits scene, Pym and Janet create a smaller version of the Quantum Realm portal that fits in the back of Luis's van. They send Scott through so he can collect quantum particles in a cannister for Ghost. Once Scott has finished, he asks to be brought back through the portal, but there's no response as Hank, Janet and Hope have turned to dust.
The second post-credits scene is just a shot of a big ant playing the drums.