Warning: Wikipedia contains spoilers.
Tintin finds a briefcase and returns it to the owner, Professor Hector Alembick, who is a sigilographer. He shows Tintin his collection of seals, including one belonging to a Syldavian king, and asks Tintin to help him arrange a trip to Syldavia for research. The seal contains the Syldavian motto, "Eih bennek, eih blavek", and a picture of a pelican.
On the plane he begins to suspect a plot. The Alembick who rides with him doesn't smoke and has different eyeglasses than the one he met with the seal collection. Then the pilot pops open a trap door and Tintin falls out and lands in a haystack.
In Syldavia, the king must possess King Ottokar's Sceptre to rule, and every year he rides in a parade showing it, while the people sing the national anthem ("Rejoice, Syldavia!/This is our king/The sceptre is his witness/Of its feats I will sing!"). The sceptre is a rod with an image of a pelican at one end.
Tintin succeeds (despite a car accident or two) in warning the king, who then rushes to the treasure room to find the sceptre missing and Alembick, the photographer Czarlitz, and a few others unconscious. Puzzled, Tintin wanders around and notices a spring cannon in a toy store. He returns to the treasure room with Thomson & Thompson and a stick the size of the sceptre and shows them that the camera is really a spring cannon in disguise.
Thomson & Thompson cross the river with Tintin and look for the scepter in the birch forest. It is found by the Bordurians, whom they follow. At the border, Tintin wrests the scepter from a Bordurian and takes a plane, which is shot down. He makes the rest of the journey by foot; Snowy runs in with the sceptre (which had fallen out of Tintin's pocket) just as King Muskar is about to abdicate.
The king makes Tintin a knight of the Order of the Golden Pelican, the first foreigner to be so honored. He also finds out that Alembick is a pair of identical twins; Alfred was substituted for Hector before leaving for Syldavia.
The Syldavian language is a Germanic language with an admixture of French and Slavic. It was written earlier in the Latin alphabet, but is now written in Cyrillic. An attempt at describing the language is at http://www.zompist.com/syldavian.html .
Like earlier albums The Blue Lotus and The Broken Ear, King Ottakar's Sceptre has a political subtext. Written in the late 1930s, the storyline reflects real-life events which were taking place in Europe at the time. The unseen ruler of Borduria is called Mustler, obviously a combination of Mussolini and Hitler, and Syldavia represents the peaceful, agrarian countries which the Axis powers were threatening.Plot Synopsis