Agent Sam Ryan wants out of her partnership with Gabriel Stern. She's tired of the paperwork and tired of being alone. Unfortunately her boss wants her as Gabe's partner but he will let her go alone to guard a government minister. Reluctant because she believes she is really being set up as bait. None the less she takes the job and will use it to investigate why the word PENUMBRA keeps coming up in her life.

Gabriel wants to be on his own, without a partner to hold him back and is thrilled that Sam is moving on. Then he learns her new assignment and is ready to rip his boss (who is also his brother) a new one. He knows the minister is a clone and could have only come from Hopeworth ... the same military facility that keeps coming up in Sam's past. He is now determined to protect her and finally begins to open up as it is discovered the connection between them is far stronger ... and more dangerous than either of them had believed.

PENUMBRA is book three of author Keri Arthur's Spook Squad and the final in the series. I find Ms. Arthur's writing style complex but still easily followed. Her characters have flaws and are realistic, even though there is usually a supernatural element, you can still believe someone like this person exists. The three books of this series follow Sam and Gabriel through their meeting until this one where there is finally a happy ending. Even if that ending left an opening a mile wide for another book should the author ever see fit. I would have liked to see a little more romance between the two of them. Also it seemed that the ending was rushed, it felt as if there was more that needed to be said but Ms. Arthur just ran out of pages. This is an e-book release of a 2009 print book but I had not read the print book so I can't say if there are any changes or additions. I have Ms. Arthur on my look for list and hope to see more offerings from her.