Remembrance of Things Past
Criminal Minds Season 6 Episode 3 (10/06/10)
A quarter century ago, a killer stopped just when Rossi got close. Now, he's developed Alzheimer's and is repeating his murders only because he can't remember them.
At first, the team assumes this is probably just a copycat doing the Butcher's thing, since the new killings are sloppier. Yet Rossi insists the Butcher is somehow involved.
A clue comes from the eighth victim, Karen, and why she didn't call anyone during the ordeal. This is because she had a son, Colby, who lives locally with Lee Mullens.
The people she would have called were there already. The team swoops in and gets to Lee Mullens, noticing his Alzheimer's, while Colby is out hunting the next victim.
Rossi cajoles him into giving up the location where Colby is, and he's busted. The Butcher admits to Rossi that he remembers him and he's the reason he stopped.