High Heat (Nikki Heat) by Richard Castle

An ISIS-style beheading of a journalist, carried out by a New York City group pledging fealty to that rogue state, becomes more than just another case for NYPD Captain Nikki Heat when the killers announce their next target: her husband, magazine writer Jameson Rook. Meanwhile, Heat is haunted by a fleeting glimpse of someone she swears is her mother... a woman who has been dead for nearly twenty years.