4x13 - Homicide: Life on the Street

Russert and Munch are assigned to work a case together; they find a retired cop who was murdered near his wife's tombstone. The dead cop's son asks Lewis, whom he went to the academy with, to get involved with case. He also makes his own inquiries, which get him into a bit of trouble. A suspect is arrested; however, despite the overwhelming evidence against the accused, the jury acquits him. The son contemplates delivering his own justice.