In Ursa Major Lake City, the death of a single member of a family of zebras by some mysterious adversary grips this city in the San Caballo mountain county. The family was healthy the day before, and now the sister is dead, and two brothers are in the grips of madness. How could this happen in this short of time? What mysterious adversary has the power to kill one zebra and cause two other ones to go mad?

Fortunate for the ponies of this small mountain city Royal Investigator Justice Silverlight is recovering in the area. Still, he not alone in this area; with him is his fiancée Princess Celestia Borealis. It will take this seasoned team to unravel the sister's mysterious deaths and the madness of the two brothers.