What is escaping from the cage on the back of that wagon?
1 - A large hostile white ape that had been destined for some menagerie.
2 - An angry imp, formerly an abused familiar, now looking for a bit of payback against anyone of arcane or holy bent.
3 - Snakes! Why did it have to be snakes?
4 - Criminals being taken to another jail or to the gallows.
5 - Undead bound for the experimental lab of a necromancer.
6 - A planned ambush, they're not escaping, they're attacking!