On a winter day, not long before Christmas, the alchemist Wittgenstein encounters the orphan girl Emily Laing for the first time on the steps of the London Underground. The old man knows immediately that he will not go home without the frightened girl, who is also accompanied by a noble rat. But soon Wittgenstein discovers that Emily harbors a much greater secret than a talking animal. And that beneath his beloved city lies another London – the ancient metropolis. A magical place full of mysterious figures and dark riddles. And everything is connected to Emily Laing and a mysterious being named Lycidas. The great fantasy classic is being reissued in a revised edition with an exclusive removable magical London map.