Favor, Affection, Malice or Ill-Will 

A guy tells Lindsay that he's been asked to find a hit-man. So they send Alvin to make contact. The man says he wants him to get the one who killed his daughter and got off. They first look into the girl's murder and the guy was a person of interest but they didn't have any evidence, so they let him go. They talk to the suspect who maintains he was there but he didn't kill the girl. He saw someone run away at the time. They find the weapon that was used. They connect it to a batch of guns that a known gun dealer got. They find the guy and arrest him. They later learn the dealer is an undercover Fed. Selling the gun was part of a operation. They learn who had the gun and try to find out if he's the killer or did he pass it to someone else. The S.A. wants them to arrest the father, but Alvin thinks he can talk the man out of going through with it because he empathizes with him. But the S.A. and Voight tell him to make him think he did it so he will pay Alvin. And Ruzek returns but ... Written by rcs0411@yahoo.com