A boy vanishes from 1983 Hawkins, Indiana, sending his friends, family, and the local police on a frantic search - one that leads to a mysterious girl and a string of unsettling clues.

As Will remains missing, Mike and his friends shelter a mysterious girl, while Joyce believes her son is trying to communicate and Hopper investigates a string of strange incidents.

The hunt for Will escalates as Joyce believes he may be trying to contact her. Hopper follows unsettling leads, and the boys shelter a mysterious girl who could be connected to their friend's disappearance.

A troubling discovery escalates the search for Will as Hopper probes Hawkins Lab, Joyce follows unsettling signs, and the boys shelter a mysterious girl who may hold crucial clues to their missing friend.

Seeking answers about Will, the boys turn to Mr. Clarke; Hopper and Joyce pursue a dangerous lead at Hawkins Lab; and Nancy joins Jonathan to investigate Barb's disappearance.

Hopper presses Hawkins Lab for answers as the boys enlist Eleven in a daring sensory-deprivation experiment to find Will. Meanwhile, Nancy and Jonathan arm themselves and set a trap for the creature.

Hopper and Joyce launch a last-ditch mission to find Will as the kids and Eleven prepare for a final confrontation - while Hawkins Lab closes in and the boundary between worlds frays.