Based on true events, Breach tells the tale of two FBI agents, Robert Hanssen (Chris Cooper), a senior member of the Soviet Analytical Unit, and Eric O'Neill (Ryan Phillipe), a young computer specialist given the task of monitoring Hanssen. It is only later that O'Neill discovers his true objective - to find proof that Hanssen has been selling secrets to the Soviets and is being financially rewarded for his actions. The contradiction of an openly religious man betraying his country, to the extent that his actions constituted the worst security leak in US history, forms the basis of the story.