The Pledge (2001)

On the day of his retirement, Nevada homicide detective Jerry Black lingers in his office one last time. But when the body of a murdered 8-year-old girl is discovered in the snow-blanketed mountains, the reluctant retiree is unable to step aside. Jerry offers his expertise at the crime scene, and takes it upon himself to deliver the devastating news to the victim's parents. The grieving mother begs Jerry for answers. Faced with the tragic nature of the crime, the parent's suffering and his own uncertainty about life after the police force, Jerry swears on his soul to find the killer. When an ambitious younger cop wrenches a dubious confession from a simple-minded suspect, the case is closed, but not for Jerry. Despite the skepticism of his peers, Jerry follows his hunch that the real killer is still at large and set to strike again. But how far will Jerry go to fulfill his promise? And at what cost?