"Eleven, are you listening?" says Matthew Modine as Dr Martin Brenner in the official teaser for Stranger Things season four.
Season three ended with what looked like the death of Jim Hopper (David Harbour), the Byers family leaving town and the destruction of the secret Russian laboratory.
The one-minute clip released by Netflix on Thursday heralds the return of the character who was last seen in season two and revealed that Eleven (Millie Bobby Brown) is imprisoned.
Set in what appears to be the Hawkins National Laboratory, children play together until Dr Brenner shows up and says: "Today, I have something very special planned for you."
WATCH IT HERE:
Entertainment Weekly reports that the new season will take viewers to Russia, where Hopper survived and is being held by operatives.
About the new season, creators Matt and Ross Duffer said a "new horror is beginning to surface, something long-buried, something that connects everything".