Booth's grandfather Hank comes to live with him and tags along as Brennan and Booth investigate ashes and charred remains found by a real estate agent while showing a property to prospective buyers. Meanwhile, Hank tries to play matchmaker for Booth and lets Brennan in on some family secrets.

When a man dressed as Santa Claus blows himself up during a botched bank robbery, Brennan and Booth work to identify the bomber and determine his motives. Meanwhile, Brennan makes plans to spend Christmas in El Salvador, but her father convinces her to spend the holidays with him and Margaret Whitesell, a newly discovered distant relative.