Trivia: At the climax of the movie when Russell Crowe confronts Senator Collins about his involvement with the death of the senate research aid, he goes outside to leave and is accosted by the assassin, Robert Bingham. Bingham is apparently going to kill Crowe when the police show up in force. Bingham raises his M-16 to shoot Crowe and the police shoot him. In the next scene Crowe is entering the news article in the newspaper's computer. The camera gives us a glimpse of the computer screen. If you pause it and read the story it says that the assassin, Bingham, is found by the police dead at his apartment from an apparent suicide instead of being shot down in a fusillade of police gunfire in front of Senator Collins' office.
Trivia: Bill Nighy, who played Cameron in the original BBC serial, was considered for the role again, before it was decided to make the character a female.
Answer: The assassin that Stephen hired to spy on Sonia found out and told Stephen. At some point off-screen, Stephen told Anne details about his affair with Sonia and accidentally told her that she was being paid to spy on and sleep with him for $26,000. Anne told Cal about the $26,000, and Cal realises that Stephen knows a lot more about Sonia's spying for Point Corp than he is letting on. If Stephen was completely innocent, there would be no way for him to know the amount was $26,000. Cal and his team of journalists never told Stephen the specific amount of money Sonia was getting.