Red Rackham's Treasure (1944) is the 12th adventure of Tintin and a direct sequel to The Secret of the Unicorn. In the previous tale Tintin and Captain Haddock had discovered three parchments revealing the location of the Unicorn, a sunken ship. Said ship contains the treasure of famed pirate Red Rackham. In this adventure, the two friends set out on a naval expedition to locate the treasure. Accompanying them are Thomson and Thompson, determined to protect them from Max Bird, who escaped from prison after the previous book (though he never shows up).The small group is joined by a stowaway, Professor Cuthbert Calculus. He is an inventor who insists that his one-man submarine is ideal for the mission. The Professor himself turns out to be very useful in locating the ship, as the centuries-old co-ordinates are less straightforward than originally thought. Calculus would become the last major addition to the cast of the series. The book is considered one of the highlights in the series and served as a change of direction for the protagonists, as by the end of the story Haddock becomes independently wealthy and the new owner of Marlinspike Hall, which becomes the main characters' residence for the remainder of the series.
- Alcohol-Induced Idiocy: Haddock drinks a full bottle of the 300-year-old rum he'd found, then dives straight back in to the ocean for more without putting his helmet back on.
- Artistic License – History: In the original French, François de Hadoque (in the English translation: Sir Francis Haddock) was given the château of Moulinsart (Marlinspike Hall) by Louis XIV as a reward for his services in 1695. The problem with that: Moulinsart is situated in the environs of Brussels, i. e. in a part of the world that at the time belonged not to France, but to the Spanish Netherlands and the Holy Roman Empire.
- Badass Boast: Tintin is flustered by all the con artists who claim to be Red Rackham's descendants and demand a share of the treasure. Captain Haddock, however, reminds everyone that he is a descendant of Sir Francis Haddock, who killed Red Rackham...and there are times when his ancestor's fighting blood boils in his veins. The con artists don't press their claims after that.
- Blatant Lies: Dozens of con artists start badgering Tintin and Haddock for a share of the treasure by claiming to be descendants of Red Rackham.
- Brick Joke: At the beginning of the book, a newspaper leaks the treasure-hunting story, causing all kinds of gold diggers to show, claiming to be descendants of Rackham and entitled to their share of the treasure. Haddock gets his revenge on the reporter at the end of the trip by letting the reporter talk his "secretary", Professor Calculus...
- Breakout Character: Professor Calculus. Hergé had been using various Absent Minded Professors as characters in previous stories. All were one-shot characters, but Calculus went on to become a recurring character, and Tintin Destination Moon, Tintin Explorers On The Moon and Tintin The Calculus Affair all centered around his achievements.
- Bungling Inventor: Calculus is presented as one of these in a bit of Early Installment Weirdness. His clothes-brushing machine costs the captain his clothes, while the Thom(p)sons get caught in a wall bed twice.
- The Cuckoolander Was Right: Calculus is a believer in divination via pendulum. The pendulum continuously indicates that the treasure is not with the ship, but somewhere else. Later on in the book, he's shown using the pendulum...and it leads him straight into the basement of Marlinspike Hall, where Tintin and Haddock have just discovered the actual treasure.
- Deserted Island: One figures prominently in the plot. Francis Haddock had once landed on the isle. Tintin and his crew find the island long deserted by humans and filled with the skulls of its former inhabitants. A large population of parrots keeps repeating the words of the 17th century visitor. At first the protagonists think this is a Treasure Island. But soon realize that nobody would hide his treasure in an island and never return to it.
- Exact Words: The Thom(p)sons get tired of always pumping air to the diving suit, so the Captain yells at them to keep pumping until he tells them to stop. Naturally, he forgets to tell them to stop after Tintin surfaces, until he investigates the creaking noise at night.
- Foreshadowing: When Haddock wonders if the treasure is hidden somewhere on the deserted island, Tintin says that the treasure's probably aboard the sunken Unicorn, since Francis Haddock would have brought it home with him when he was rescued. As it turns out, he did bring it back, hiding it in Marlinspike Hall.
- Gadgeteer Genius: Professor Cuthbert Calculus and his specialized submarine.
- Game Changer: From this story onward, Haddock and Calculus live a life of luxury in Marlinspike Hall, with most stories beginning or at least taking place partially there. Although Tintin himself doesn't move into Marlinspike Hall, we almost never see his old apartment in any of the following adventures.
- It's the Journey That Counts: The treasure is not with the wreck of the Unicorn as first believed, but it does allow for old documents associated with the ship to be recovered, as well as some other components of the ship (such as the figurehead) and of course the rum. Also, Professor Calculus's submarine was successfully tested, and this allowed Calculus to gain a great deal of money from the endeavor. The treasure itself was in Marlinspike Hall, the Haddock family's old estate (and where Tintin was imprisoned in the previous book)—which Professor Calculus purchased with the proceeds of the submarine test, and the nature of which was made clear by the aforementioned documents.
- Loud of War: Captain Haddock's Identical Grandson status is confirmed when it's discovered the island parrots transmitted Francis Haddock's insult litanies over the years, and they find a native idol representing the captain, mouth wide open in one of his tirades.
- Nailed To The Wagon: Unintentionally. Captain Haddock's onboard supply of whisky is replaced with the components of Professor Calculus's submarine. He had been previously told by his doctor that he was suffering cirrhosis and was told to lay off the alcohol, but Haddock was ignoring the advice. From the time his last bottle of whisky vanished, to his discovery of the rum in the wreck of the ship, Haddock was forced to go dry.
- No Antagonist: Unusually for a treasure hunting story of this type, nobody opposes the heroes in their search for Rackham's treasure. The possibility of Max Bird getting involved is brought up, but it never actually happens. The closest thing to a villain here is a shark that attacks Tintin while he's diving.
- Pirate Booty: The title already indicates that the story is about the treasure of a pirate. Red Rackham and his pirates were introduced in the The Secret of the Unicorn.
- Reality Ensues: At one point, Tintin thinks Haddock might have buried the treasure at the foot of a cross on the island, but eventually comes to realize that this was implausible; if he'd managed to get the treasure off the ship, he'd have taken it with him when he was rescued later on.
- Shipshape Shipwreck: Averted. The wreck of the Unicorn has decayed considerably.
- The album is read by Kramer to his son in Kramer vs. Kramer.
- Spirou and Fantasio: In the album Le Groom Vert-de-Gris, a re-imagination of Spirou set during the Nazi occupation of 1942, Fantasio gets stuck in a similar fully automatic machine for cleaning clothes as the one used by professor Calculus in Red Rackham's Treasure.
- Sustained Misunderstanding: Due to Calculus' hearing problem, when the captain shakes him demanding to know what happened to his crates of whiskey, he thinks they're talking about his submarine.Haddock: Where is it!?
Calculus: Onboard, of course!
Haddock: My whiskey is onboard! Praise the Lord!
Calculus: Naturally, it's in separate pieces...
Haddock: Separate pieces? My whiskey's in separate pieces?
- Threatening Shark: Until Tintin gets it drunk on three-hundred-year-old rum. Calculus' grinning shark sub is also mistaken for the real thing.
- Treasure Map: Averted. While this is a treasure hunt story, the co-ordinates of the sunken ship are not part of a map. They are written on three parchments and have to be deciphered. The protagonists originally thought that the Sir Francis Haddock calculated them based on the Greenwich Meridian. Tintin correctly figures that the French naval officers under Louis XIV were using the Paris Meridian as their reference point.
- What Happened to the Mouse?: Max Bird, the villain of the previous story, is mentioned to have escaped from prison. Thomson and Thompson suspect that the man is seeking revenge and could be hiding aboard the treasure-hunter's ship. That convinces the two officers to volunteer their services in this journey. In the end, this plot point seemingly just serves as an excuse to get Thomson and Thompson into the story. By the time the story concludes, there is nothing to indicate that Max was ever aboard the ship. Or even near it. The Thom(p)sons claim he was "discouraged by their presence". Max never appears in any later stories, either. His fate is never resolved.