When two children, Becca (Olivia DeJonge) and Tyler (Ed Oxenbould), visit their grandparents (Deanna Dunagan, Peter McRobbie) for the very first time, it seems like a great chance to connect and have fun with long-lost Nana and Pop Pop. But before long, the children discover that their grandparents act more than a little strange after 9:30pm. What happens when this cheerful visit turns terrifying?