The children of Stranger Things face a terrifying monster from the Upside Down in the first full trailer for the new series of the hit sci-fi adventure.

Set in summer 1985, as the residents of Hawkins, Indiana, frolic in the pool, the footage for the upcoming episodes promises “one summer can change everything”.

The trailer opens with the group surprising Dustin (Gaten Matarazzo) with a welcome home banner after he is spooked when all his remote control toys start moving in the same direction.

As they hide in the shadows waiting to jump out at him, it can be seen that Eleven (Millie Bobby Brown) has a nose bleed.

Despite the high jinks it becomes clear things have changed as Mike (Finn Wolfhard) can be heard saying in voice-over: “We’re not kids any more.

“What did you think? We were just going to sit in my basement all day and play games for the rest of our lives?”

The clip also shows the return of Winona Ryder as Joyce Byers and David Harbour as Sheriff Jim Hopper, who can be heard telling her: “It’s important to me that you feel safe. I want you to feel that this can still be your home.”

David Harbour and Winona Ryder in Stranger Things (Netflix)

The trailer reaches a climax with the appearance of the monster baring its teeth and roaring.

Stranger Things will return to Netflix on July 4.