There is a serial killer on the loose preying on vulnerable women. The only identifiable mark the killer leaves are letters - sometimes one, sometimes two - all carved into the torsos of his victims. Together, they spell “Sydney”. When he grabs Daisy Dawson, he believes he has found his next victim. But despite her small stature, she fights back with an expertise that quickly frees her. Before fleeing the scene, Daisy also manages to grab what proves to be crucial evidence: a necklace from around the killer’s neck.

Carmen Sanchez is a tough Homeland Security agent who plays by the rules. But when her sister is attacked, revealing a connection to a series of murders across Southern California, she realizes a conventional investigation will not be enough to stop the ruthless perpetrator. With nowhere else to turn, Sanchez enlists the aid of Professor Jake Heron, a brilliant and quirky private security expert who, unlike Sanchez, believes rules are merely suggestions. The two have a troubled past, but he owes her a favor and she’s cashing in.

When a woman is found brutally murdered on Austin’s lakeside hike-and-bike trail, investigative reporter Bailey Rhoads turns up on the scene demanding access and answers. She tries to pry information out of the lead Detective Jacob Merritt, but this case is unlike any he’s ever seen, and nothing adds up. With the pressure building, Jacob knows the last thing he needs is a romantic entanglement, but he can’t convince himself to stay away from Bailey.

Haunted by the serial killer she never caught, Detective Kimberley King leaves her job in New York and relocates to the sleepy town of Dead Woman Crossing, Oklahoma. Kimberley hopes to bring her daughter Jessica up close to her family, far from the bad memories the city holds. But her quiet new home is not the peaceful place she dreamed of. Within days of her arrival, Kimberley is called to the scene of a terrible crime: her friend Hannah, a single mother, has been brutally murdered while her one-year-old daughter was sleeping nearby.

Forensic genealogist Rowan Healy has made a name for herself by helping investigators trace the family trees of violent criminals who have eluded justice for years. But the pressure of police cases left her burned out, and she’s shifted her focus to helping adoptees find their biological parents.