The Cornwalls Vanish (previously published as The Cornwalls Are Gone) (Amy Cornwall, 1)

A phone rings with a terrifying ultimatum: locate and liberate an unnamed captive in forty-eight hours, or her kidnapped husband and ten-year-old daughter are dead.

Now, and in open defiance of Army Command, Amy must employ every lethal tactic she has to save them. To succeed, she must discover not only who dispatched her on this mission, but why. Without her family, she's dead anyway.