As Nightmare Night comes to Ponyville, Twilight and the other girls are tracked down by Pinkie Pie, who is ecstatic to tell them that they've all been invited to her uncle's manor for one of his world-famous Nightmare Night parties. They meet old and new faces as everyone begins to mingle.

But late that night, a horrible laugh and a bloody scene awaken the guests from their slumber, and they find themselves trapped inside of the house, at the mercy of a psychotic killer. As more and more ponies disappear and slip into this psycho's clutches, it's up to Pinkie Pie and her faithful sidekick Twilight Sparkle to solve the Case of the Brindlehoof Killer.

A dark comedy murder mystery, with lots of ponies and far more characters than Da Rules say I can list. Rated Teen for pony death, blood, and one count of irreverent mishandling of a corpse.

(Credit for Sherlock Pinkie goes to C-H-Loboguerrero-C on deviantart)