Blue Bloods - Season 2 Episode 10 -

A man who is a confidential informant working for Erin is killed. So she has Danny investigate to find out if he was killed because it was discovered he's an informant and if so how? And when a video that shows a police officer beating up someone comes out, Frank looks into it. First he talks to the officer who says that video was edited to make it appear he was rough on the man. He then learns that the source of the video is man who has it in for the NYPD and tries to get him to give the actual video.