Without a Trace (Athena Force, 25)

U.S. Coast Guard Lieutenant Nikki Bustillo has tracked her target to the bowels of a phantom ship—and she refuses to lose the scent now. But when her overseas contact is brutally murdered on the streets of Hong Kong, Nikki's manhunt is compromised. The mission came from the higher-ups at her alma mater, Athena Academy, and failure isn't an option. Her only hope: the help of a maverick, martial arts expert, police detective. Nikki and her new partner will follow the enemy's shadowy trail out of the ocean and to the ends of the earth—even after their invisible foe turns the skilled trackers into vulnerable prey.