In the interim years between the first Ant-Man and this one, Scott has become estranged from daughter-father duo Hope van Dyne and Hank Pym (Evangeline Lilly and Michael Douglas). He's been housebound with an ankle monitor, making time to play with his daughter and open up a security business with his pal Luis (Michael Peña). Meanwhile, the Pyms have been -- oh, you know -- building an elaborate contraption to rescue Hope's mother, Janet van Dyne (Michelle Pfeiffer), from the Quantum Realm, where she's been trapped for 30 years after going "subatomic" in her Wasp suit. Casual! Scott is entirely disconnected from this, but gets an eerie vision of Janet, and, lo, he's pulled into the machinations.
Ant-Man and the Wasp's narrative is extremely contained. Both our heroes and their foes just want access to the lab that Hope and Hank have built, which, by the way, can shrink into handy suitcase size. The ostensible main villain Ghost (Hannah-John Kamen) has designs to use the technology to heal herself. An accident from her childhood involving the Quantum Realm has rendered her partially non-corporeal and caused her extreme pain. She thinks if she can access it -- which Hope and Hank are trying to do to save Janet -- she can stop the agony. Still, even though she has beef with Hank, she’s hellbent on getting better, not destruction. So, yeah, no one here is out to take over the world, which isn't to say the movie is completely devoid of dramatic tension. It refreshingly tends to arise from a more emotional place, even if Ghost's backstory is slightly under-baked.
Still, you also really aren't coming to this for a lot of nuance. It's not a chamber drama -- or even Black Panther, for that matter -- and admittedly the pace tends to slow down the more serious the circumstances get. That's all the more noticeable because the rest of plot is executed with such a sense of zippy glee.