"Mac Is a Serial Killer" follows Frank (Danny DeVito), Dennis (Glenn Howerton) and Dee (Kaitlin Olsen) as they start to suspect that Mac (Rob McElhenney) is a serial killer terrorizing Philadelphia. Charlie (Charlie Day), on the other hand, attempts to prove Mac's innocence by using techniques he's gleaned from watching too many legal TV shows.Read all of Variety’s story on the matter here.