FBI junior agent Eric (Ryan Phillippe) was recalled from a peripheral mission by headquarters and ordered to monitor Robert (Chris Cooper), the head of the FBI Information Security Department, who was suspected of treason. Robert had been dealing with Soviet agents for more than 20 years, but there was evidence that Robert had been selling intelligence to the other party in recent years. So Eric monitored Robert as a full-time assistant. As the two people's interactions deepened, Eric felt that Robert's tough and capable style and harmonious family atmosphere were quite different from the words of his boss when assigning tasks. In order to dispel Eric's doubts, the FBI disclosed the background of this mission to him. Eric realized that he had become one of the key participants in the investigation of the biggest betrayal in the history of the FBI. However, facing such a far-sighted opponent, Eric must carefully use every bit of Robert's trust to find direct evidence in the last two months. This film is adapted from real events.