Lots of similar films made in recent years
these are all similar in plot and tone:
MARTHA MARCY MAY MARLENE - riveting, haunting, relentlessly suspenseful... Elizabeth Olsen's debut and an unforgettable performance at that!
KILL LIST - one of the most terrifying, mind-bending, and ambiguous films ever... watch it with subtitles though otherwise the Scottish accents, particularly with this film, are almost totally indecipherable
THE CONSPIRACY
SOUND OF MY VOICE
similar in plot but not in tone:
FAULTS (darkly humorous)
RED STATE (action elements as well as satire/dark humor)
GREEN ROOM
similar in tone but completely unrelated plot:
THE GIFT (2015)
BLUE RUIN