After moving into an apartment building, a young woman finds herself in the middle of experiencing strange and horrifying events.

A man dies mysteriously in the woods. Moments later he is stalking and murdering someone in a completely different environment. Meanwhile, a small group of strangers are stuck in an infinite loop. Is the killer some kind of doppelgänger? Is a mysterious social media "Challenge" responsible for his actions? Is the infinite loop the center of alternate universes taking and sending people randomly to other universes?