Challenge of the Werethief

Crime! Police ran through the streets of Priscarbs but the news ran faster, the news that the Curtains of Heaven had been stolen from the residence of the Dowager Duchess of Vernaseges. Those pearls were worth more than half the city, and now they were in criminal hands.
Whose hands? Who else but Hisfendivarius the Werethief? Any daring crime was credited to that mysterious maestro of robbery whose true appearance was unknown. The hoi polloi would say Hisfendivarius stole the sun to explain a cloudy day and laugh at the police for letting him get away.
This time, though, it was true. The Dowager Duchess's servants reported seeing a hawk, a monkey, a cat, and a slithering snake. The police knew what that meant, but not what to do about it. Inspectors and custodes ran hither trying this and thither looking for that, each method seeming as good as any other when it came to catching a thief who had never been caught. Inspector Iagius had his own theory.
"Falgunus, if that thief has gone so much as a dozen yards away, I've never learned a thing in all my years on the job. But I think I have, and I think he hasn't."
"Yes, sir. What do you want me to do then, sir?"
"Have your restraints in hand and be ready to act on my word."
The inspector and the custos crept around the robbed residence, looking for a culprit who could look like anything. The wonder was not that Hisfendivarius stole the Curtains of Heaven, but that it took him so long to get around to it when his techniques were unopposable.
"Hold on a moment, Falgunus. I must tighten up my laces. I'll quit tomorrow if I trip tonight. Just stand right there if you would while I . . . Now! Get that zebra!"
Custos Falgunus twisted around and tossed his loop over the neck of the inconspicuous zebra behind him which struggled and spat and turned into a man. Hisfendivarius!
"You finally slipped up, my lad. If only you knew that zebras don't live here. I only know what one is because my little ones love the zoo so."
The crestfallen Hisfendivarius shook his head. "I don't know what a zebra is. I don't pick what I turn into, you know. It's just always worked out until now is all."
Another impossible case solved by Inspector Iagius!