Accompanied by her husband, son and daughter, Adelaide Wilson (Lupita Nyong’o) returns to the beachfront home where she grew up as a child. Haunted by a traumatic experience from the past, Adelaide grows increasingly concerned that something bad is going to happen to her family.

Her worst fears soon become a reality when four masked strangers descend upon the house, forcing the Wilsons into a fight for survival. When the masks come off, each stranger takes the appearance of a different family member.