The film stars real-life married actors Dave Franco and Alison Brie as Tim and Millie.

Together follows Tim and Millie, a long-term couple with a struggling relationship.

They move from the city to a remote countryside town for Millie's new job, as she seeks to take the next step in their relationship.

The horror begins when they go for a hike and fall into a mysterious cave, where they encounter a supernatural force that triggers their bodies to merge in painful ways.