Twelve-year-old Perigee has never met a problem they couldn't solve. So when their Dad's spirits need raising, Perigee formulates the Plan: a road trip to Dad's childhood home to reunite him with his estranged mother. There's something in it for Perigee, too, as they will finally get to visit "Eklunds' Puzzle House," the mysterious bed & breakfast their grandparents built but never opened.

They arrive ahead of a massive storm and the House immediately puts Perigee's logical, science-loving mind to the test. Corridors shift. Strange paintings lurk in the shadows. Encoded messages abound. Despite Perigee's best efforts, neither the House nor Grandma will give up their secrets. And worse, prickly Grandma has outlawed games and riddles of any kind.

Even the greatest of plans can crumble, and as new arguments fill the air, the House becomes truly dangerous. Deadly puzzles pop up at every turn, knives spin in the hallways, and staircases disappear. The answer lies at the heart of the House, but in order to find it, Perigee and their new friend Lily will need to solve a long-lost, decades-old riddle... if the House itself doesn't stop them first.