Together

Millie Wilson lands a job teaching elementary English and moves to the countryside with her longtime boyfriend, Tim Brassington. Shortly before the move, Millie proposes at a going-away party, but Tim hesitates to respond, leaving her mortified. The scene sets up growing tension in their relationship as they prepare for a new life apart from their past.

During a rainstorm, they fall into an underground cave while hiking and decide to camp inside for the night. Tim drinks from a pool of water, but Millie refuses. Tim recalls traumatic details of finding his mother in bed with his father's decaying corpse, a memory that haunts him throughout the night.

Upon waking the next morning, they discover their legs are partially fused together. They separate, choosing not to acknowledge the strange incident, and attempt to move on with their day. The moment plants a seed for the bizarre, unexplainable events to come.

Tim begins experiencing episodes where he is inexplicably drawn to Millie, creating confusion and fear for both of them. He visits a doctor who dismisses the symptoms as panic attacks and prescribes muscle relaxants. The doctor also mentions that a local couple, Simon and Keri, recently went missing, hinting at danger nearby.

Millie's coworker Jamie McCabe visits to welcome them to the neighborhood and invites him to dinner. The couple recounts their experience at the cave, explaining it was once a New Age church before it caved in. The conversation deepens the sense of mystery surrounding the cave.

Millie drops Tim off at the train station for a gig, but Tim experiences another episode and drags himself to Millie's workplace. In a bathroom stall, they have sex, after which their genitals become stuck together. After painfully forcing themselves to separate, Jamie spots them.

Millie visits Jamie's house to apologize and Jamie offers her some water while discussing Aristophanes' theory of eros and the idea of an 'other half.' He encourages her not to let go of her 'other half' and shares memories of his seemingly deceased husband. The conversation plants the philosophical seed that love can complete a person, even as danger looms.

Using exif data from their social media photos, Tim discovers that Simon and Keri visited the same cave after noticing the same symbols. He tries to persuade Millie that they may suffer the same fate, but she remains skeptical. The discovery deepens their fear and sense of inexorable fate.

That night, Tim and Millie are supernaturally drawn together again, causing their bodies to contort until their arms fuse. They manage to stop further fusion by consuming Tim's pills before falling unconscious. The threat of fusion lingers as they slip into sleep.

Tim awakens tied to a chair, and Millie uses a saw to sever the fused limb in an attempt to free them. They scramble to plan their next move, hoping to reach safety, though the immediate danger of the fusion remains.

Millie enters Jamie's house and finds a television showing the wedding tape of two men she does not recognize, followed by a ritual in which the men fuse together. Jamie, revealed to be the product of fusion, promises they are happier after becoming whole and urges Millie to complete the fusion with Tim. When she resists, he cuts her arm the same way his constituents had their arms cut in the tape before she escapes.

Millie reunites with Tim in their driveway. He mentions the creature he saw in the cave as the result of resisting fusion, and he proclaims he does not want to end up like them. He prepares to slit his own throat to save Millie.

Millie's wound from Jamie nearly causes her to bleed out, but Tim saves her by fusing his arm to her wound. Accepting their fate, the two affirm their mutual love and slow dance to the song '2 Become 1' as they fuse into a singular being. That weekend, Millie's parents arrive for a visit and are greeted by the fused Millie and Tim, a seemingly normal, androgynous being.