In the small town of Twin Crossing stands a House on a line between reality and insanity. It’s sustained by the souls it has spent centuries Splitting. Otto von Kraus in the middle of World War II hid inside the House, not realizing his decision would change his life forever. He became the Gatekeeper, forced to live as both child and man, occupying the same body and space but not at the same time, effectively losing his sense of freedom. Elder and Younger Otto live within its walls, charged with protecting a Cane - their life source - and preventing anyone from passing through the House and into the Parallel, the place where the other half of the Split souls live.
Both Ottos and the House rely on each other for survival, until one day Elder Otto witnesses what a Splitting looks like for the first time. Disturbed by the painful event, he decides to make amends by reuniting the separated souls, even if it means killing himself in the process.
With the help of Olive, a precocious child, and Archibald, his long-time friend from the Parallel, they take on the dangerous task of uniting souls the House spent centuries Splitting. When not every union turns out the way they expect, they are left to question if what they’re doing is causing more harm than good.
Who will win the war between good and evil - and how many innocent souls will be lost in the process?