The Devil's Apprentice

the long version

"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 in his cloven footwear or destroy them. Assisted only by an aspiring teen 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"--Publisher's description.