The Adventures of Tintin #8

Tintin finds a lost briefcase and returns it to the owner, Professor Hector Alembick, who is a sigillographer, an expert on seals (as in the sort used to make state documents official). He shows Tintin his collection of seals, including one which belonged to the Syldavian King Ottokar IV. Tintin then discovers that he and Alembick are under surveillance by some strange men. Tintin's flat is even bombed in an attempt to kill him. Suspecting a Syldavian connection, Tintin offers to accompany Alembick to Syldavia for research...