Soldier of Fortune (Soldiers of Fortune #1)

The secret enemy.

J.D. Brettman was armed, dangerous and out for revenge. One of Chicago's top attorneys, his appetite for adventure and years as a mercenary soldier were past—until his sister was kidnapped and taken to Central America. J.D. vowed to rescue his sister at any cost, but he needed someone he could trust at his side....someone like his assistant, Gabby Darwin.
 
In the lawless tropical forests, they shared both danger and desire. There Gabby came face-to-face with the demons that haunted J.D.'s restless soul--and learned that her love was his true and most feared enemy....