A family reunion turns into a full-on massacre when a gang of masked killers invade a sprawling country mansion on a ruthless mission of murder. Paul (Rob Moran) and Aubrey Davison (Barbara Crampton) are about to celebrate their wedding anniversary, and they've invited their grown-up children out to the country to share in the revelry. The first to arrive are Crispian (A.J. Bowen) and his new girlfriend Erin (Sharni Vinson). It isn't long before the rest of the family has filed in as well, and the party gets under way. Later, at the dinner table, old sibling rivalries begin to resurface and parental preferences quickly become apparent. Just as tensions begin to flare up, however, a crossbow arrow blasts through the glass window and panic sets in.