Criminal Minds: Season 2, Episode 22

2 - 22: Legacy

When homeless people begin mysteriously disappearing from the streets in Kansas City, a local detective who believes that something sinister is afoot calls the BAU to investigate the disappearances and from the evidence gathered, the BAU determine that the detective is right in his worries and they also believe that the UnSub is someone who is "cleaning house" which means fixing what he believes is wrong with the world and the homeless people he regularly snatches off the street are his victims.