A town has a festival every year in the dead of winter. The festival of birds. The towns folk dress in feathery robes and beaked masks and dance and frolic in the belief that the changes of the seasons are controlled by the presence of birds. According to tradition, the festival tricks Spring into coming early because the birds have returned.
The characters are given the task of transporting a flask of highly volatile liquid a long distance. The flask cannot be shaken too much or it will explode. The adventure involves stormy sea-voyages, bumpy cart rides through densely populated towns and horseback combat. In short there are many opportunities for it to break and explode.