Can a movie about a super hero that can shrink to the size of an ant actually be good? You decide.

Years ago, at S.H.I.E.L.D. headquarters, a very angry Hank Pym approaches Howard Stark and the other leaders of SHIELD complaining that they are trying to steal his research on Pym particles. He refuses to allow the research to be potentially misused by others and vows that SHIELD will never get it, and officially quits working with them.

In the present day, cat burglar and savvy tech worker Scott Lang reaches his final day in prison, having served his sentence for stealing from a corrupt business and transferring the money back to the people they had swindled. On the outside Scott finds it difficult to find and keep a job as an ex-con, and the lack of money for child support keeps him from being able to see his daughter. His roommate and ex cell mate, Luis, tells him that he has discovered the perfect mark for another burglary. Scott want’s to go clean, but after his employer finds out he lied about being a con and fires him he feels he has no choice but to accept. Luis and Scott put together a small team and set about robbing an old man’s safe while he is out of town. Unfortunately the only thing Scott finds in the safe is a weird suit.

Meanwhile, Hank is invited to attend a meeting at Pym Enterprises, now being run by his protege Darrin Cross and his own daughter, Hope, to witness the announcement of a new project: the Yellow Jacket. Cross has discovered Hanks old research and footage of his time as the Ant Man, and claims that he can make his own shrinking suit, and that it will be an advanced military weapon like the world has never seen. Hank and Hope meet up to speak in secret, realizing that they need to do something to stop Cross quickly before he can complete his research.

While trying to discover why the suit was kept in such an advanced safe, Scott decides to try the thing on, and accidentally activates it, shrinking down to the size of an ant, and is knocked around through the various rooms in his apartment complex while the voice of Hank Pym throws unhelpful remarks and riddles at him. When he is able to return to normal size he immediately breaks back into the house to return the suit, only to be arrested on the way back out. In the jail he is visited by Hank, claiming to be his lawyer, and is told to take opportunities when they arrive. Back in his cell he sees a group of ants march in, and suddenly the suit expands on the floor. He quickly puts it on and makes his escape while shrunken, riding on a winged ant and eventually passing out from the heights.

Scott wakes up back in Pym’s house, under Hope’s watching eyes. Hope and Hank tell Scott about Cross’s plans to create a new weaponized shrinking suit, and convince him to help them break in to steal it back. As Scott is trained on how to use the suit, and communicate with his new ant allies, Cross continues to perfect his version of the Pym particle, making the Yellow Jacket suit operational and ready to sell to the highest bidder. During the training, Hope becomes increasingly frustrated that Hank won’t simply let her use the suit so they can do the mission without needing to involve Scott, but Hank eventually reveals that he lost his wife, Hope’s mother, in a scenario when she needed to use her own suit as the Wasp, to shrink to stop a nuclear weapon, and ended up shrinking forever, trapped in the quantum realm. He simply couldn’t let himself risk the same happening to his daughter.

The final stage of Scott’s training is a field mission to retrieve a piece of needed technology from an old SHIELD warehouse, but when Scott arrives he discovers that the warehouse has since been converted into the new Avenger’s base. He has to fight his way past the Falcon, but is able to successfully escape with the tech. On returning to Pym’s house the three agree that they are ready for the mission, but a surprise visit from Cross puts them on edge, and a paranoid cross tells Hope that he is increasing security before the sale of the Yellow Jacket. With the new complication Pym and Scott are forced to bring in additional help from Luis and his crew, and a new infiltration plan is hatched.

As the sale of the Yellow Jacket commences, Hope and Hank arrive for the final demonstration as Scott, Luis, and the others get into their positions to take out the company. The infiltration goes well enough, with Scott and the ants placing explosives to blow up the building, and wiping out the computer backups of the research, but when they attempt to steal the Yellow Jacket they find that Cross is onto them, and he traps Scott, threatening his family, Pym, and Hope. Scott is able to break free and rescue Hope, but Hank is shot and wounded, and Cross takes the Yellow Jacket and flees for the roof to a waiting helicopter. Scott fights past Cross’s security guards to follow, managing to catch up at the last moment as the building explodes, despite the death of his favorite ant, but Cross has suited up as the Yellow Jacket himself, and the two begin a desperate size changing fight, eventually being thrown from the helicopter and landing in a backyard pool. Yellow Jacket is thrown into a nearby bug zapper and is temporarily out of commission, but Scott manages to get arrested again and is thrown into the back of a squad car, leaving Yellow Jacket loose.

A police dispatch alerts Scott and the arresting officer, his ex-wife’s new husband, that there is an incident going on at his family’s address and they rush over. Scott is able to get his helmet back on, allowing him to shrink out of the handcuffs and break past the police blockade to reach his daughter’s room, to find Yellow Jacket waiting for him. He fights Cross, attempting to keep his daughter safe from harm, but when he sees no other choice he realizes that the only thing he can do is destroy the Yellow Jacket from the inside, which will force him to disable his regulator and shrink to subatomic size. He does so to save his daughter’s life and destroys Yellow Jacket, the damage causing Cross to crunch down into nothing, as Scott disappears into the quantum realm. Somehow his daughter’s voice is able to let him retain his mind just well enough use a growth disk on the regulator, allowing him to return to the normal world, although with no knowledge of what he had seen during his trip.

After his heroics Scott finds him welcomed back into his family’s lives. Hope and Hank strengthen their father daughter bond, and Hank gives her the new prototype suit he had been working on with her mother, the upgraded Wasp suit. And Scott finds out that Falcon has been asking about him, trying to track him down.

TLDR: Criminal Scott Lang is tapped by Hank Pym to become the new Ant Man and stop a maniac inventor from creating and selling an new shrinking suit.