David Mathews, the wildly popular candidate expected to win the Colorado governor's seat, has been murdered. His death has made headlines across the nation and Denver's police are scrambling to solve the high-profile case. Mathews's estranged wife Sydney had motive--her husband's infidelities--and when the gun used to kill him is discovered in the couple's mountain home, Sydney is arrested and charged with first-degree homicide.

Catherine McLeod is covering the story for The Denver Journal and receives a call from an anonymous woman claiming she saw the real killer leave the...