When, in 1940, Saul Prior receives a letter from Lady Caroline Degabaston to catalogue the library of Thool Abbey in Hertfordshire, he jumps at the chance. But he soon finds himself in a realm that seems cut off from the real world. In the cryptic fastnesses of the abbey, Prior is beset by bizarre dreams and seems incapable of leaving the place. Lady Caroline proves to be a baleful and mysterious presence, and Prior is mired in a landscape that...