The graduate wizards of the High Energy Magic building of Unseen University are conducting an experiment in teleportation across worlds, normally accessible only via L-space. With Skazz and Tezz in place as guinea pigs test subjects, the test goes off almost without a hitch. Now, the wizards race against time to find out what has happened and fix it. Until then, Lord Havelock Vetinari is trapped in the Victorian London of Sherlock Holmes, in the unhappy custody of Dr. Watson, while Holmes finds himself in a world of magic and narrative causality rather than cold logic. Oh, bugger...