A mysterious murder of a US Senator in Washington D.C. bearing the distinguished marks of a Soviet assassin code-named Cassius, forces retired CIA operative, Paul Shepherdson, to team with rookie FBI agent, Ben Geary. Shepherdson is convinced his nemesis is long dead. Meanwhile, Agent Geary, who wrote his Master's thesis on Shepherdson's pursuit of Cassius, is certain that he has resurfaced. As Shepherdson and Geary work their way through crimes both past and present, they discover that Cassius may not be the person they thought him to be, forcing both to re-examine everything and everyone around them.