To Love a Cop (Harlequin Super Romance Book 1980)

She's sworn to protect her heart 

After what Laura Vennetti and her son have been through, she's avoided all contact with the police. Then her son brings detective Ethan Winter into their lives. Despite how appealing—and gorgeous—he is, it's safe to say Ethan isn't her dream man. 

Immediately, though, Laura can see how different he is from her late husband. Ethan is thoughtful, considerate and a good influence on her son. Add in the intense attraction between her and Ethan… The temptation to give in is irresistible. To her surprise, Laura feels the wounds of the past healing, making her wonder if she could love this cop forever.