Dr Sabian Blake - astronomer, scientist, and master of the Cabala - is in possession of the Nemorensis, an ancient leather-bound book which holds the secrets of the universe. Its mysterious inscription reads: 'Wormwood...the bright star shall fall from the sky...and many will die from its bitterness'. Deciphering this prophecy could prove the key to saving London from a catastrophic fate. But there are others interested in the Nemorensis too - for more sinister reasons.