Philip Hart, a fortysomething Norfolk school teacher, has sought solace in drink as he sees his life start to unravel. He suspects, with good reason, he is about to lose out on a promotion to a younger colleague who is assumed to be sleeping with his wife. And one night, driving home drunk from a village pub, he knocks down and kills an old man fleeing from a nearby mental hospital.
To avoid blame Hart hides the body in a roadside culvert, but guilt forces him to learn the identity and background of his victim, so he can make some kind of amends. On a visit to the mental hospital he discovers clues to a decades-old mystery somehow involving the inmate, prompting him to sever all ties with his previously cloistered existence.
Adopting the role of Percival, the holy fool of legend charged with finding a redeeming relic, Hart's journey takes him very far from Norfolk, into Sweden's sub-arctic wilderness and to one of the continent's forbidden places. And also back to that darkest of times, when the world was at war and aflame.
But if the man he killed had been driven mad by his part in creating this mystery, so Hart is in danger of becoming just as deranged. He has gone beyond needing simply to atone for a single death. He is now on a mission to rekindle what in his increasing obsession he believes is nothing less than the light of the world.