After solving her first case, Siobhan O'Brien faces her biggest challenge yet – Thanksgiving! With her lawyer boyfriend Craig in tow, Siobhan travels to Minneapolis to endure small talk with the extended O'Brien clan and chow down on some seriously delicious turkey and dressing. Everything's swell until her sister-in-law Gwen tells her about her brother Sven's frequent late-night meetings with his co-workers. Since Siobhan's next case is just a ferry ride from their house in Washington state, she asks for Siobhan's help.

Big sister is happy to oblige, though she's got her hands full. Hired by Phillip Ahn, a Korean artificial intelligence genius with his own personal island in the Pacific Northwest, Siobhan enters the strange, sequestered world of the uber rich, where Ahn, his wife, his two ex-wives, and his five children all live under the same gilded roof.

Ahn brings Siobhan to his estate because he swears that Duke, his youngest child and only son, is an impostor. Is Ahn crazy, or is Duke really someone else? And could it be possible that Sven's troubles are somehow linked to Ahn's? As Siobhan digs into these dangerous mysteries, she learns that family secrets have some very Deep Roots.