Alana and a group of college seniors board a party train for a Halloween-themed bash, but their fun spirals into fear when a mysterious assailant begins killing the passengers one-by-one.
When Pippa and Thomas move into their dream apartment, they notice that their windows look directly into the apartment opposite – inviting them to witness the volatile relationship of the attractive couple across the street. But what starts as a simple curiosity turns into full-blown obsession with increasingly dangerous consequences.