Happening upon a briefcase lost in the park Tintin returns it to its owner [[AbsentMindedProfessor 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 [[{{Ruritania}} Syldavia]] and offers Tintin a job as his assistant. Tintin declines but later finds himself under surveillance by sinister individuals who seem connected with that country. After more than one attempt on his life Tintin decides to accept Alembick's offer and accompany him to Syldavia and get to the bottom of things.

Tintin soon finds himself thrust into the middle of a ruthless conspiracy to overthrow King Muskar XII of Syldavia in the interests of their fascist neighbor Borduria. Faced with traitors at every turn, Tintin has to race against time to save the King's throne. If the stolen King Ottokar's Sceptre is not returned by St. Vladimir's Day, the King will have to abdicate and the Bordurians will invade...

''King Ottokar's Sceptre'' was written in 1938 and 1939 and was written in the light of the threat of fascism; the Bordurian plot has parallels with Anschluss of Austria and Syldavia's location is reminiscent of Albania (invaded by Mussolini in 1939). Both Syldavia and Borduria would play important roles in later adventures and the story also introduced the recurring characters of Bianca Castafiore and the villainous Colonel Boris Jorgen.

* AbsentMindedProfessor: Professor Alembick.
* ANaziByAnyOtherName: The Bordurians - though they also have elements of other 1930s fascists.
* AntiquatedLinguistics: The Syldavians and Bordurians actually speak a distorted version of Marol dialect, dialect spoken by Flemish people in Brussels.
* ArtShift: Hergé mimicks medieval miniature painting in the tourist brochure.
* AsideGlance: Tintin actually winks to the reader on the last page.
* BlackShirt: Almost literally.
* CreatorCameo: Creator/{{Herge}} and his then assistant Edgar P. Jacobs (''ComicBook/BlakeAndMortimer'') can be spotted in military uniforms attending the royal reception at the palace.
* CreatorProvincialism: The royal palace of Syldavia is modelled after the one in Brussels, Belgium. The language spoken by the Syldavians and Bordurians is based on the Marol dialect, spoken by Flemish people in Brussels.
* DinosaurDoggieBone: Snowy steals a bone from a dinosaur skeleton at a museum.
* DoesThisRemindYouOfAnything: The [[TheGhost unseen]] leader of the conspiracy is named [[UsefulNotes/BenitoMussolini Müss]][[UsefulNotes/AdolfHitler tler]].
* EasyAmnesia: The Syldavian spy at Tintin's house.
* EvilChancellor: Colonel Boris.
* [[spoiler: EvilTwin]]
* GeorgeLucasAlteredVersion: In the original version the uniforms of the royal guards looked totally different. They were changed to uniforms looking like the Beefeater uniforms worn by royal guards in the United Kingdom.
* TheGoodKing: King Muskar XII is clearly devoted to his people, and is even willing to abdicate rather than try and keep power through bloodshed. [[spoiler: Fortunately Tintin manages to defeat the conspiracy and save his throne.]]
* GorgeousPeriodDress: The uniforms of the Syldavian royal guards.
* IAteWhat: Tintin's reaction when he's told the Syldavian meal he's eaten includes dog, and [[EatTheDog Snowy is missing]]. Snowy comes [[BigEater out of the restaurant's kitchen]] moments later.
* ImpliedDeathThreat: Tintin gets one in the form of a Syldavian proverb on his restaurant bill.
* ImprovisedParachute: Involving an actual parachute.
* LockedRoomMystery: How was the Sceptre stolen?
* MakeItLookLikeAnAccident: Tintin is almost "shot while trying to escape". He only does escape by throwing himself headlong down a steep slope.
* MeaningfulName: Averted with Professor Alembick, unlike most scientist Punny Names in Tintin--an alembic(k) is a piece of alchemical/chemistry apparatus, while Alembick is a Sigillographer.
* OutOfCharacterMoment: When Tintin meets Professor Alembick at the start, he's constantly smoking. He doesn't smoke at all for the rest of the book, which Tintin notes. [[spoiler:This is a clue that he's been replaced by an impostor]]. It's the other way around in the animated version where he suddenly starts smoking.
* TheQuisling / TheMole / DoubleAgent: A disturbing number of Syldavians are in Bordurian pay.
* ParanoiaFuel: [[InvokedTrope It seems like]] Tintin can trust no one in Syldavia and at one point even begins to wonder if even Professor Alembick has been replaced by an imposter. [[spoiler: He has.]]
* PunnyName: General Stassanow is a pun on the Belgian milk brand ''Stassano''.
* RedAlert: What the King essentially orders nationwide when Tintin warns him of Borduria's plans to invade.
* ReferencedBy: ''ComicBook/BlakeAndMortimer'': In ''The Voronov Plot'' the restaurant ''Klow'' and its owner from ''King Ottokars Sceptre'' appear.
* RippedFromTheHeadlines: When this story appeared in syndication in 1939 the Second World War was already on its way. Nazi Germany has occupied Austria in 1938 and invaded Poland in 1939. Thus the threat of Syldavia being occupied by Borduria in this album by a man named ''Müsstler'' had a very real context.
* RoyalsWhoActuallyDoSomething: King Muskar XII drives his own car and knows how to use a gun to protect himself.
* {{Ruritania}}: Syldavia and Borduria. Syldavia in particular is often ranked as one of Hergé's greatest achievements - an extremely detailed and well researched fictional nation with it's own history, flag and language.
* VariableTerminalVelocity: Snowy falls slowly enough to get caught in the opening parachute deployed from Tintin's chair.
* YouKnowTooMuch: There are a number of attempts to kill Tintin once he starts meddling.