The Chemist

By Stephenie Meyer

She was called Juliana until she found herself in the crosshairs of a corrupt government agency. Now she sleeps with one eye open and a pocketful of fake identities. Currently going by the alias Alex, she is a young, brilliant scientist, best at what she did for the government, but apparently someone decided she knew too much and needed to be silenced.
Alex hates her new life on the run, never trusting anyone, always looking for her assassin. So when her old boss tracks her down and promises to call off the dogs if she will do one last job for him, against her better judgment, she agrees, pressured by the desire for a normal life and by the even stronger desire to prevent a terrorist from releasing a virulent, deadly disease upon the nation.
Her old boss points Alex in the right direction and she is able to locate the terrorist. But he just doesn't look like the kind of man who would be a mass-murderer. In fact, he seems kind, gentle and basically decent. (Also very good-looking.)
So she kidnaps the man, Daniel, using her particular set of unique skills and interrogates him. But no torture she inflicts upon with her chemical potions is able to get him to confess where he has stashed the deadly disease. And he continuously denies any knowledge of anything about a disease, insisting he is a just an ordinary guy who teaches school for a living. The interrogation is interrupted by hired killer who crashes her torture session to rescue Daniel. Turns out the new guy is Daniel's black-ops twin brother Kevin whom Daniel thought was deceased. And he is highly upset that Alex is torturing his brother. In the struggle that follows, Alex's hidden defenses take Kevin (and his killer dog) down and she is able to secure him and his dog.
Like Alex, Kevin used to work for the government and then became a liability. His old boss and her old boss got together and hatched a scheme that would have the two of them efficiently eliminate each other. Poor Daniel was nothing but a pawn to lure the two of them in. But due to Alex's foresight, they both survive the encounter and put their heads together to take on the bad guys who are trying to take them down.

This was a gripping, exciting story. Alex is a very resourceful, highly competent heroine who, despite her diminutive size, comes out the victor, eventually. She usually is the one who saves the day in any deadly encounter. Together, she and Kevin are a match for anything their ex-bosses try to throw at them.  Yet, despite her deadly past, she and Daniel fall hard for each other, with brother Kevin looking on in disgusted bemusement.  So this is part thriller, part spy novel and part romance story and a really fun and engaging read.

Kirkus Reviews rated it "B for Badass": https://www.kirkusreviews.com/book-reviews/stephenie-meyer/the-chemist/.