When another noble turns up without her head, Twilight takes this as a sign that all of Equestria is in peril. Teamed up with an odd detective from the Canterlot PD, can she piece together what's going on before everything else falls apart?

This first story in the annals of What In the Name of All That Is Pony? features ponies not thinking, blind obedience, and things just generally taking turns for the worse.
Also, OC ponies.