The Nightman Cometh
"The Nightman Cometh" is the thirteenth and final episode of "It's Always Sunny in Philadelphia"’s fourth season . 
<triplet> The Nightman Cometh <subj> It's Always Sunny in Philadelphia <obj> part of the series <triplet> It's Always Sunny in Philadelphia <subj> fourth season <obj> has part <triplet> fourth season <subj> It's Always Sunny in Philadelphia <obj> part of the series