In Edinburgh, 1886, the brutal murder of a university professor, coming soon after the killing of a retired lighthouse keeper and quickly followed by a bizarre exhumation, has the entire city on edge. Carus Groves, a conceited and prejudiced police inspector, is assigned the case. Baffled by the superhuman strength required to rip two men apart and drag up a coffin, Groves latches on to the odd behaviour of an anguished young woman, Evelyn Todd, who claims to have dreamed of the crimes in great detail. Meanwhile, two unlikely friends - Thomas McKnight, a jaded Professor of Logic and Metaphysics, and Joseph Canavan, a compassionate cemetery attendant - are drawn inexorably towards Evelyn and the secrets of her tormented psyche. They discover her extraordinary imagination was violently suppressed in childhood, but in her dreams she retains the image of 'the lamplighter' - whose presence outside her orphanage she heard each evening, and whose face is concoction of all the friendly men she knew. Evelyn now insists the killer is this lamplighter. And as a strange beast gallops through Edinburgh's misty alleys, and Groves's investigation flounders, McKnight and Canavan use the only weapons they possess - reason, logic, intuition, philosophy and sheer luck - to unearth the secrets buried in the dark recesses of Evelyn's mind...