Detective Cassie Maddox is still trying to deal with the events of In the Woods. She is out of the Murder Squad and has started a relationship with fellow detective Sam O'Neill but is too badly shaken to commit to Sam or to her career. Then Sam is allocated a new case, that of a young woman stabbed to death just outside Dublin. He calls Cassie to the murder scene and she finds the victim is strangely familiar. In fact, she is Cassie's double. Not only that, but her ID says she is Lexie Madison the identity Cassie used, years ago, as an undercover detective. With no leads, no suspects and no clues, Cassie's old undercover boss spots the opportunity of a lifetime: to send Cassie undercover in the dead girl's place. She could pick up information the police would never hear and tempt the killer to finish the job. So Cassie moves into Whitethorn House, poses as a post-grad student, and prepares to enter Lexie's world.

塔娜‧法兰奇，爱尔兰知名小说家。从小由于父亲工作的关系，迁徙过多个国家，直到1990年才定居都柏林。因为经常搬家，接触不同文化，使得她的观察力也远比一般人敏锐。

她在都柏林的三一学院接受专业演员训练，并曾参与戏剧、电影、配音等工作，而这些经历也帮助她能够成功模拟角色的各种样态。其长篇小说处女作《神秘森林》以睿智、细腻、优雅的叙事手法和纤毫毕现的人物刻画获得全球各地书评的一致赞誉，不仅荣获“爱伦坡奖”、“安东尼奖”、“麦可维提奖”、“巴瑞奖”等四项“年度最佳处女作”大奖，更跃登纽约时报、出版家周刊、今日美国报、旧金山纪事报、洛杉矶时报、丹佛邮报、波士顿环球报、Book Sense、北卡独立书商协会等全美九大畅销排行榜，并入选亚马逊网络书店2007年度编辑推荐选书。此后法兰奇的第二部小说亦再次席卷国际文坛，并同样入选亚马逊网络书店2008年度编辑推荐选书。