On this week's Person of Interest…

Reese infiltrates a drug smuggling ring but learns that the person of interest, Cahill, is an undercover cop.

Unfortunately, someone knows that there is a snitch in the group because of their police connection.

Finch sends Fusco to destroy Cahill's undercover file before anyone else can get to it. A fellow police officer, Davidson, catches Fusco in the act and reveals that he is the informant.

Reese tricks the group leader, Vargas, into thinking he is the undercover cop.

The group makes the drop and meets with L.O.S. Cahill reveals himself and captures L.O.S. and Reese and Carter assist in taking down the group.

Cahill learns that L.O.S. is CIA but he chooses to take him in anyway.

Mark Snow gets him off and then has him killed.

Reese saves Fusco from being killed but demands that Fusco take the fall for the murder so he can become indebted to the dirty cops. Fusco reluctantly agrees.