The mysterious murder of a US senator bearing the distinctive trademark of the legendary Soviet assassin "Cassius," forces Paul Shepherdson (Richard Gere), a retired CIA operative, to team with rookie FBI agent, Ben Geary (Topher Grace), to solve the crime. Having spent his career chasing Cassius, Shepherdson is convinced his nemesis is long dead, but is pushed to take on the case by his former supervisor, Tom Highland (Martin Sheen). Meanwhile, Agent Geary, who wrote his Master's thesis on Shepherdson's pursuit of the Soviet killer, is certain that Cassius 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 always thought him to be, forcing both to re-examine everything and everyone around them.