CSI: NY Season 7 Episode 22 (05/13/11)
After a close call struggling with a suspect Mac decided to look into the one unsolved case sitting on his desk. The case involved a robbery gone wrong, both suspects fled the scene and the police could never catch up to them.
The reanalysis of a coin purse placed a girl in the bodega where the robbery took place. Mac interviewed the girl's mother who had never stopped looking for her daughter. He used the information to get a new lead on the whereabouts of the suspects. One of the robbers was located, but he did not have the girl with him. He told Mac he parted ways with his partner after he tried to kill the girl.
A sample of the second suspect's handwriting was posted nationwide and used to locate him. He was raising the girl he had kidnapped from the robbery as his daughter. He was killed by police and Mac eventually reunited the girl with her mother.
With the case solved Mac confided in Jo that he wondered if he had done enough good.