Secret of Platform 13, Paperback by Ibbotson, Eva; Porter, Sue (ILT), ISBN 0141302860, ISBN-13 9780141302867, Like New Used, Free shipping in the US

Cornelius the wizard, Gurkintrude the fey, Hans the ogre, and Odge Gribble the hag only have nine days to search London, locate the kidnapped prince, and return him to the Island before the passageway to their magical kingdom will close, and they will not be able to return for nine years