Spoilers for Stranger Things season 2 episode 8.
The creatures break into Hawkins Lab, forcing Hopper, Owens and the others to retreat. Mike realises that the shadow creature can follow them through Will, so Joyce sedates her son. A power failure leaves the survivors trapped behind locked doors. Bob volunteers to restore the breakers and use the security computer, while Owens guides him over the radio. His work opens a route outside and lets the waiting group enter the grounds. Bob nearly reaches Joyce in the lobby, but a creature catches him before he can escape. Hopper pulls Joyce away as more creatures descend on Bob, killing him.
The survivors regroup at the Byers house. Dustin compares the shadow creature to a Mind Flayer from Dungeons & Dragons, while Mike argues that it controls the creatures and tunnels as a single hive mind. They disguise a shed so that Will cannot recognise their location, then wake him and recall memories from his childhood. Will responds beneath the possession by tapping Morse code with his fingers. His message tells them to close the gate. A ringing telephone gives away where they are, and the approaching creatures force everyone to prepare for another attack. One crashes through a window, already dead. The locks on the front door slide open, and Eleven walks into the house. She and Mike see each other again.