The Devil is retiring... but who's taking over? When teenage Pen inherits the job of caretaker for a London building with no doors and only a secret entrance from the caretaker's lodge – which she must never use – little does she know it will lead her into unbelievable danger. For Azmordis, also known as Satan, a spirit as old as time and as powerful as the Dark, Immortality is running out.

In the house with no front door, a group of teenagers are trapped in assorted dimensions of myth and history, undergoing the trials that will shape them to step into his cloven footwear – or destroy them. Assisted by only by an aspiring teenage chef called Gavin and Jinx, a young witch with more face-piercing than fae-power, Pen must try to stop the Devil's deadly game plan – before it's too late.

By turns very funny, very scary and always thrilling, this is an incredible return to YA for Siegel.