"The Last Thing He Told Me" by Laura Dave

Before Owen Michaels disappears, he manages to smuggle a note to his wife of one year: “Protect her.” Hannah Hall knows exactly to whom the note refers: Owen's sixteen-year-old daughter, Bailey, who wants absolutely nothing to do with her new stepmother. After the FBI arrests Owen's boss, a US Marshal and FBI agents arrive at her Sausalito home unannounced, and it’s clear Owen isn't who he said he was. And Bailey just may hold the key to figuring out Owen's true identity—and why he really disappeared.