London's exorcists! I have a reward for all of you, a job for one of you. Come to Brierley House, 20th April, 9.00am." The newspaper ad is a baited hook and it smells like a three-day old corpse. But hey, it's a grand in hand just for turning up so Felix Castor goes in anyway, alongside the curdled cream of his dubious profession. And once he's in it's hard to get out again. Brierley House is the home of Russian oligarch Gavril Ustinov, now missing, his driven daughter Ksenia Ustinova and their staff of taciturn, sinister domestics. It also hosts an invisible force that attacks exorcists and negates their abilities--a force that seems to be centuries old. Ksenia wants Castor to locate her missing father, alive or dead. Castor wants to find out who set a trap for exorcists back in the late Middle Ages and what else they were up to. For a job this big he's got friends he can call on: zombie data-fence Nicky Heath, reformed succubus Juliet Salazar, jaded cop Gary Coldwood and Trudie Pax, the Anathemata's finest warrior. But the ghosts of Brierley are many, and they won't give up their secrets lightly...