King Ottokar's Sceptre

Herge'

Ah, Syldavia, made-up country where one can get into endless trouble if one is a young Belgian reporter. Tintin and his newfound friend Professor Alembick head to Syldavia to study the country's governmental seal, for Alembick is an authority on such things. Problem is that while they're there, the country's crown and sceptre are stolen, seemingly by Alembick, and Tintin, along with Thomson and Thompson (they all became friends again at the end of the last volume, natch), have to figure out where the sceptre is, where Alembick has gotten off to, and why the seemingly harmless absent-minded professor had such a sudden change of heart.

More of the series' development to be found here, as Herge got farther away from using real places (and offensive caricatures of their inhabitants, for which he later apologized) and started using fictional places as allegories. I hadn't read the Tintin books since they were serialized in Children's Digest in the seventies, and I must say I'm rather surprised at how well these have held up over the years. Very good stuff.