County detective Simone Fitzhugh discovers a series of seemingly unrelated deaths that look like heart attacks but are really murders. Her husband, retired detective Michael Demidov, realizes the murders are related and suggests that Simone go to the FBI. Past history with the Feds (The Unlikely Assassin) makes Simone wary, but the FBI surprisingly enlists their help. Demidov's innovative interrogation techniques help unravel a tangled web of illegal drugs, a gunrunning militia, and a sinister terrorist plot to bring down the US government, all hatched by a shadowy figure called The Spider. The detectives' lives are further complicated when Demidov's Russian mafia family tries to draw the estranged son back into the fold. With Simone's help, Demidov manages to extricate himself from the clutches of his family, but the consequences prove to be both a great boon and a heavy burden.