Operation: Midnight Tango is Linda Castillo’s first Harlequin Intrigue after several Silhouette Intimate Moments and four mainstream romantic suspense releases. It’s always nice to see an author who doesn’t turn her back on her series romance roots after finding success in single titles. It’s even nicer when she brings the same skill to her series books that she’s demonstrated in her bigger books. Sadly, that’s not the case here.

Zack Devlin is an agent with a top-secret unit of the CIA called MIDNIGHT. An unusually high number of prisoners at the Bitterroot Super Max Prison in Idaho have turned up dead under mysterious circumstances, and Zack was sent in undercover as a prisoner to find out the reason. Early one morning before dawn, two guards arrive at his cell and demand he accompany them to the infirmary. Besides the odd timing, Zack knows going to the infirmary can only be bad news, because prisoners have a tendency to go in for minor injuries or none at all and not come out. He manages to get away from the guards, and captures corrections officer Emily Monroe, forcing her to help him escape.

Emily came in to the prison early that morning to investigate her own suspicions about the fate of several prisoners. Zack tells an incredible story about experiments being done in the infirmary that seems to prove her right, except she knows she shouldn’t trust anything he says. Her own father was a corrections officer at the same prison who died in disgrace years earlier after he had an affair with a female inmate. As Emily starts to feel an attraction toward Zack, she starts to wonder if she’s repeating her father’s mistakes.

This is an exciting read that provides nonstop action, but little depth. The relentless pace might be enough to satisfy some readers. It’s certainly never boring, as the characters race from the prison across the snowy Idaho countryside. Castillo knows how to keep her story moving, and that’s exactly what it does from start to finish. The author is adept at suspense, and the action sequences are all well-executed. The story does have more of a mainstream edge than most series books, which helped boost the tension and keep it exciting. What it does not provide are characters worth caring about or any real surprises in its action-packed plot.

Castillo takes the easy way out when it comes to character development. Zack has his sob story about his past and Emily has hers, and that’s really all there is to them. It would be one thing if they had strong enough personalities that they still came across as vivid characters despite the lack of information revealed about them, but they don’t. He’s a standard-issue secret agent type; she’s the usual damsel in distress who too often seems like she’s not all that bright. More than once, I wanted him to tap on her forehead to see if there was a hollow sound inside. They generate some decent sparks as a couple, but the romance bumps along in fits and starts. This is one of those books where they kiss, then one person says they shouldn’t do that. Later they kiss again, and then the other person says they shouldn’t do that. And then it happens again. There are good reasons why they shouldn’t be jumping into bed right away, but this just felt repetitive and drawn out. The book ends on a nicely romantic note that would be much more effective if these characters had an ounce of depth.

This is a pretty straightforward plot. The hero and heroine figure out what the villains are up to, the villains try to kill them to keep anyone else from finding out, the hero and hero run around trying not to get killed. It’s a basic romantic suspense plot that would work just fine, except the author tries to generate mystery where there is none. In the very beginning, two of the villains are identified and we learn they’re conducting some kind of medical experiment on the prisoners that results in death. It seems clear-cut enough. But there are a couple of other villains who the author makes a point not to identify, except there are so few characters in the book it’s obvious who they must be. In the end there are some big revelations I suspected were supposed to be surprising, but weren’t. If a story’s going to be predictable, the author might as well deflate the expectations and reveal everything up front, rather than set the reader up for disappointment.

After a promising beginning, Operation: Midnight Tango turned out to be just another shallow series romance. It looks to be the first in a new series, with another entry coming in December called Operation: Midnight Escape (which seems like it would have been a good title for this book, but no matter). Hopefully it will be better. As for this book, it’s a serviceable read, but too hollow to be a truly good one.