Allegiances oleh Cynthia Eden

An old enemy returns…with a new victim in the conclusion of The Battling McGuire Boys by New York Times bestselling author Cynthia Eden 

Private investigator Sullivan "Sully" McGuire has a reputation for danger. He's spent most of his life tracking the men who murdered his parents. The one woman who sees past Sully's predatorial pursuit is the wife he abandoned years ago. But Celia James has returned, this time with a target on her back. In order to save Celia, Sully is forced to resurrect old demons. New dangers–and dormant desires–bring Sully and Celia closew…and old enemies even closer.