The Cop's Missing Child - Karen Whiddon (HRS #1719 - Sept 2012)

Small-town cop Mac Riordan lost his wife in a car crash, but his infant son survived, only to later be kidnapped. Now, five years later, Mac locates him living in Anniversary, Texas, with beautiful Emily Gilley. The more he gets to know this mysterious mother of his son, the less he's convinced she's a coldhearted kidnapper. She might be a victim just as much as he is. So when Emily's under-the-radar lifestyle is suddenly discovered, Mac comes clean. The threats against her -- against their child -- escalate and Mac must risk it all to protect his son…and the woman who's brought him back to life. 

Very good book.  After five years of searching for his kidnapped son, Mac has finally tracked him to Texas.  He has moved to town with the intention of finding out more about the woman posing as the boy's mother.  When he meets Emily, she doesn't seem like the type of person who would steal a child from a hospital.  When she starts receiving threatening letters, and Ryan is nearly kidnapped, Mac steps in to help protect her.  As things get worse, he finally confesses his suspicions to her, nearly ending the growing relationship between the two of them.  I really liked both Emily and Mac.  Mac gave up his job as a cop in New York to continue the search for his son.  When he came to Anniversary, he set up his trucking business and tried to find a way to get to know Emily.  When he did, his protective instincts kicked in because of the threats against her.  He was torn because logic said she was probably involved in the kidnapping, but his gut was telling him she was innocent.  He could also see what a good mother she was and how much Ryan loved her.  He also found himself attracted to her, and picturing the three of them as a family.  Emily has spent the last several years trying to outrun her past.  Her late husband had been a criminal, and now someone from that past has found her and is threatening her son.  She distrusts Mac at first, but when he starts working for the sheriff's department he is first to help her.  As he works with her to find out who is stalking her and threatening her, an attraction starts to build.  She sees how good Mac is with Ryan, and how hard he is working to help her.  When she finds out that he has come to town believing that he is Ryan's true father, she is stunned and terrified that he will try to take Ryan away from her.  When the threats against her and Ryan come to a head, he is there for her and makes her understand that he would never take Ryan away, that he only wants to be part of their lives.  The exposure of the bad guy was a complete surprise to me.