S2·E20 The Golden Gate Cop Killer: Part 1

A cop from San Francisco who's a friend of Dan's comes to Vegas. It seems that someone is targeting cops, sending them messages telling them when they will be killed usually with a number in it. The man follows the cop and kills him in front of Dan. Dan notices two women when his friend was killed. Dan decides to go to San Francisco and is shunned by the police department but decides to investigate nonetheless and sees the women and later learns that they're cops who were sent by his friend's boss to keep an eye on him. Their boss wants Dan to leave but upon learning that he made some discoveries decides to let Dan stay.