Visiting her crusty 79-year-old aunt in northern Iowa, Marley Clark attempts to save a billionaire when he tumbles from a double-decker tourist boat captained by her cousin. The victim—founder of a biotech empire—is dead before his body hits the water. Soon Marley is consoling the widow, an old college friend and a prime murder suspect.

As Marley becomes embroiled in the murder investigation, members of the tycoon's family perish faster than overripe fruit, and the arrogant head of an international security firm renews an old vendetta. When it appears the murder spree may tie into biological weapons and terrorist threats, Marley's former Pentagon boss joins the probe.

To unmask the villains and protect her kin, Marley reaches deep into her bag of tricks, taps relatives' homegrown resources, and debates the wisdom of trusting a handsome attorney with a suspicious past and a killer smile.