CSI: NY Season 7 Episode 21 (05/06/11)
The crime lab was attacked by Raymond Harris, the convict with a grudge against Mac and his former partner Bill Hunt. The investigation took a bizarre turn when Harris walked into the police precinct to file a complaint against Hunt.
As the investigation intensified Mac discovered that Hunt had stolen money from evidence taken after they had arrested Harris. Meanwhile, the police discovered the body of the drug dealer that Harris used to work for.
A photo taken at Harris' former apartment clued Mac in to the real reason for his quest for revenge. When Bill Hunt had gone back for the money he had stolen he murdered Harris' girlfriend when she walked in on him in the apartment.
Mac arrested Hunt, and was then ambushed by Harris. After a shoot out Harris and Hunt were both killed.