Cassie Maddox, former Murder detective now working in Domestic Violence, is blindsided when a corpse is found that could practically be her twin. Not only that, the dead girl's ID says she was Lexie Madison- an ID which Cassie created for an undercover case early on in her career. That case ended when Cassie was stabbed by a drug dealer she had been tailing for weeks. Lexie was killed by a stab wound in almost exactly the same place. When Frank Mackey, head of undercover, suggests that Cassie slid into the space left by Lexie's death to investigate her murder from the inside, Cassie is unable to say no. So begins her time at Whitethorn House, playing the role of a Trinity College post-grad student, living in a dilapidated manor house with four friends as close as siblings. It is highly likely that one of these charming, intelligent people killed Lexie, and Cassie is supposed to be figuring out which one. But the longer she lives in Lexie's life, the more she wants to stay in it forever. This book sucked me in, hard. I spent a week doing almost nothing by reading. It's been almost four years since I read In the Woods, Tana French's first book and the first in the Dublin Murder Squad series, so my memories of that book's ending are hazy. No matter. This book is darkly, seductively compelling, a bittersweet delight of a story.