It's Always Sunny in Philadelphia - Season 3 - Eps 10: Mac Is a Serial Killer
After Mac arrives to the bar with scratches on his neck and exhibiting strange behavior, Frank comes to the conclusion that he is the serial killer terrorizing young women in Philadelphia. Frank sets out with his trusty chainsaw and a doubtful Charlie to find evidence to implicate Mac in the murders. In search of another suspect, Dennis and Dee do a little role-playing in order to help themselves better understand who they might be dealing with.
About It's Always Sunny in Philadelphia

Title: It's Always Sunny in Philadelphia
First Air Date: 2005-08-04
Last Air Date: 2023-07-19
Status: Returning Series
Rating: 8.279/10 (from 1129 votes)
Language: EN
Seasons: 17
Total Episodes: 169
Network: FX FXX
Genres: Comedy
Production Companies: 3 Arts Entertainment, Bluebush Productions, FX Productions, RCG Productions
Synopsis
Four egocentric friends run a neighborhood Irish pub in Philadelphia and try to find their way through the adult world of work and relationships. Unfortunately, their warped views and precarious judgments often lead them to trouble, creating a myriad of uncomfortable situations that usually only get worse before they get better.
Cast

Charlie Day
Charlie Kelly

Glenn Howerton
Dennis Reynolds

Rob McElhenney
Ronald 'Mac' McDonald

Kaitlin Olson
Deandra 'Dee' Reynolds

Danny DeVito
Frank Reynolds