Happening upon a briefcase lost in the park Titin returns it to its owner Professor Hector Alembick, an expert in sigillography (the study of seals - the ones on letters rather than the ones with flippers). Professor Alembick is travelling to the Balkan kingdom of Syldavia and offers Tintin a job as his assistant. Tintin declines but later finds himself under surveliance by sinister individuals who seem connected with that country. After more than one attempt on his life Tintin decides accept Alembick's offer and accompany him to Syldavia and get to the bottom of things.