we meet adult Pym working out of a private lab. he works for the Van Dyne corporation. initial scene is a visit from Vernon Van Dyne w/ his daughter in tow. Pym's withdrawn and clearly bored with straight science. Janet finds some way to get rid of her father. short, more personal, conversation with Pym; attempting to get him to open up by mentioning Maria.
segue to Elias Star and Monica Rappaccini at some fancy restaraunt. we learn that Elias, a complete sociopath, also works for Van Dyne but has been behind several information leaks. Monica represents Advanced Idea Mechanics. she specializes in biotoxins. Elias is looking for a better job and sees A.I.M as the way to get it. Monica shows him the specs for a game changing weapon. they need something Pym is working on to complete it.
they arrange for someone with no connection to Elias or A.I.M to break into Pym's private lab. that individual, Scott Lang, finds what he's looking for and only escapes after discovering the Ant-man costume.
Pym finds his lab ransacked. just at that moment, Janet shows up. with her is Nick Fury. they explain that they've been monitoring his activities and research; as well as A.I.M. Janet, on top of being a wealthy socialite, is also revealed to be a trainee agent (all information gathering). Pym resents their involvement. they task him with retrieving his equipment (while not stated, Fury considers to be a test). they provide him details on A.I.M and the recently released ex-con/pawn who burglarized his lab.
Pym goes hunting. Jan follows.
Lang delivers the package. they, of course, attempt to kill him; as payment. Scott is believed to be dead and a fugitive.
Pym tracks Lang down. short Ant-Man vs Ant-Pawn fight. Scott briefly explains his situation. Pym, Jan, and Scott all head to one of A.I.M's headquarters to save the day.
they all fight some interesting looking AIM mercs. Pym has it out with Elias Starr (who lets him know that Maria died in a bomb blast meant for Hank). Monica Rappaccini and Janet have one of the most vicious fights in cinema history. Scott works his way through the facility to find the antidote he needs to save his daughter's life (Monica infected her with some kind of slow-acting death virus or something). he briefly encounters George Tarleton. the latter thanks him for (unexpectedly) also stealing the ant-man costume. he thinks that he's been able to reverse engineer pym particles. he injects himself and it ends badly (setting up M.O.D.O.K).
yadda yadda Scott gives the ant-man costume back, thanks Pym, and tells him that he has an interview at Stark Industries. Fury, Janet, and Hank have a sit down; discussing their future. it's suggested that Jan will get the Wasp upgrade (Pym shows her the designs he had for Maria becoming his superhero partner). Fury tells him that the Avengers Initiative could use Ant-Man as their eyes and ears. Pym says that he'll consider the offer but that he might want to think "bigger." *thumbing a vial marked Giant-Man*