On an island akin to Portpatrick (Scotland), Anne Adams, a librarian recovering from a car crash that killed her brother, steps on to the grounds of Winterbourne. The island is owned by the largely absent Lucien Broussard, its only permanent inhabitants are the Coopers, an odd pairing of gruff brother and sister who live in a cottage by the jetty. Anne will live in the vast house alone. The library is magnificent, with priceless first editions, a librarian's dream. However Anne's early weeks in her new job are beset by obstacles - no internet, the house plunged into darkness every night when the generator is switched off, the swarming of moths in the library, and two near-fatal accidents. And then there are unexplained mysteries on the island such as the figure in the lighthouse, a freshly dug grave - and the unaccountable disappearance of the previous librarian who started the catalogue. Broussard visits, he and Anne dine together, they discuss literature and she falls for his charm. And then she discovers a secret room off the library, full of horrendous banned books - and the diary of the missing librarian whose experiences at Winterbourne mirror her own in an uncanny way. She learns the dangerous and shocking truth about her employer and Anne finds herself alone and frightened, but with no way of escaping the island.