“Could there be a less promising match?”

Well into “Girl Missing,” Adam Quantrell poses this question. Quantrell is a New England blue blood, the CEO of a prosperous pharmaceutical company. He has just visited the city’s low-income projects with the story’s protagonist, Kat Novak, a city medical examiner who grew up in the projects and is looking for answers to three drug overdose deaths. While there, Kat’s car gets stolen and she and Quantrell are viciously assaulted.

“After all these years, I finally admit to the possibility of romance, and look who inspires it. A woman who almost gets me killed over some beat-up Subaru.”

Tess Gerritsen’s novel “Girl Missing” has been re-released 20 years after it first appeared as “Peggy Sue Got Murdered.” It’s a mystery romance novel, as were her first nine books. She speculates in the introduction that few of her fans are probably aware that she got her start in romance.

Gerritsen, who lives in Camden, got hooked on romance novels while reading them as an escape from the stress of being a young doctor in a hospital. She decided she’d try her hand at mystery romance. Harlequin published her first book, despite the fact that there were 13 murders in it – a record for the publisher.

She describes “Peggy Sue,” her seventh book, as a “bridge” novel that ultimately carried her fully over to the thriller genre. Her first thriller, “Harvest,” published in 1996, became a New York Times bestseller. To date, her books have sold 25 million copies in 40 languages.

“Girl Missing” is more mystery than romance and succeeds best as such. Novak pursues her hunch that the overdose deaths are an epidemic of sinister proportions. She crosses paths with Quantrell when one of the “Jane Does” has clutched in her death grip a matchbook with his phone number written inside. The two get off to a suspicious start when Quantrell wants to go to the morgue to view the body, but isn’t forthcoming as to why. It later comes out that he is searching for his missing, rebellious stepdaughter. He is relieved he doesn’t find her at the morgue.

Kat and Adam – a less promising match? It would seem so. But romance that goes against type makes for dramatic tension. He lives in a mansion with a butler and wonders what she thinks of him, but he concedes that he really doesn’t want to know. He is attracted to her, in part, because she is fearless and a survivor. He makes forays with her into the dark netherworld of the projects where she was raised, and she with him into his world of snooty friends, classy cars, and political connections. The fact that Kat comes to suspect the unidentifiable narcotic that is killing people comes from Adam’s labs adds to that tension.

“Girl Missing” is not as taut as Gerritsen’s signature thriller series featuring Detective Jane Rizzoli and medical examiner Dr. Maura Isles. Romance dulls the bite. That said, it is well-plotted and well-told. “Girl Missing” provides a look back at where Gerritsen started, but it is where it’s taken her that’s significant.

Frank O Smith is a Maine writer whose novel “Dream Singer,” a finalist for the Bellwether Prize, will be published this year. He can reached via www.thewritinggroup.com.