In 1986, three kids mysteriously died after knocking at the door of 59 Oakwood Lane. The case was never solved. The killer never locked away. The urban legend says that anyone who knocks on that door again will meet the same ghastly fate. On Halloween night, Grace (Wynonna Earp’s Dominique Provost-Chalkley) and her friends ignore that superstitious warning and instead, they knock knock, knock.