Tintin and Capt. Haddock are returning from a movie, when they have an unexpected meeting with General Alcazar. Alcazar speaks very little, saying that he is in a hurry. While leaving, he drops his wallet. Tintin retrieves it and tries to return it to him, but by then, he's out of sight.
Tintin searches for him at a hotel, but fails to locate him. They open his wallet to find some peculiar photographs of fighter aircraft. Tintin rings up a location given in Alcazar's wallet, but fails to locate him there.
They come home to find the pesky Abdullah up to his pranks. The captain is told that he has come from Israel, sent for safe-keeping by his father. Abdullah makes Haddock furious.
Next morning, the Thompsons come to Marlinspike. They are on Alcazar's tail. They inform Tintin of Alcazar's deal with a man named Dawson, in smuggling aircraft.
Tintin sees Alcazar chatting with Dawson in a hotel. He decides to follow Dawson and comes to a warehouse complex. But a cheap trick of Abdullah's makes Tintin flee from the crime-scene. Tintin comes home and decides to go to Wadesdah. The Captain agrees to accompany him.
They fly to Khemed, but are rounded up and sent back to Beirut. Unbeknownst to them, a time-bomb is on the plane. Suddenly the aircraft's engine catches fire and the pilot is forced to land. After all the passengers have escaped, the bomb explodes, luckily harming none.
Tintin and Haddock decide to travel to Wadesdah by foot. Midway, the Captain falls asleep. Tintin keeps him quiet, while a patrol passes by. Later, they get inside the town and meet Senor Oliveira De Figuera. Oliveira hides them and says that they have a price on their head, also promising that he will get them out of the place safely.
Next morning, Tintin and Haddock disguise themselves as ladies and go out of town. They take Snowy inside a pitcher. They are met by a horse-man who takes them away.
En-route to Emir Ben Kalish Ezab's place, tanks and Mosquitoes follow them. But a mis-communication leads to the party's miraculous survival. They reach the Emir's place. They learn from the Emir that slave-trading is taking place under the orders of a Marquis De Gorgonzola. They decide to take him out.
Next morning, Tintin and Haddock set sail on a light ship. But they are suddenly attacked by two Mosquitoes, Tintin manages to shoot one down, causing the pilot to bail out. They leave the ship, now afire, on a raft. They rescue the pilot, who introduces himself as Skut.
Later, they are spotted by passengers of Gorgonzola's ship. They are hauled up and meet Bianca Castafiore. Gorgonzola decides to dispose of them. Next morning, he transfers them to another cargo ship, The Ramona. Tintin and Haddock come face to face with Alan, an old enemy. Alan tells them that he will take them to Wadesdah.
At night, the ship's engines catches fire. Alan and his crew abandon the ship. Haddock and Tintin hose down the fire and get the Ramona started. They find Skut unconscious. He wakes up and tells them of the fight with Alan. Suddenly they hear shouts. They find many Muslims being carried as slaves. Haddock brings them up but they attack him, mistaking him as a bad man. Tintin explains the situation to them.
A slave trader comes by. The captain is furious and picks up a fight with him. A faithful Muslim disarms the slave-trader. He goes away. Haddock warns the Musims that if they go to Mecca, they will be sold as slaves. They agree not to go.
Gorgonzola orders a submarine to target the Ramona and blast her out of the sea. Tintin sees the submarine advance and alerts the Captain. The captain saves the ship with skillful and calculated moves. Meanwhile, a destroyer picks up an S.O.S. sent by Tintin. It offers to help them. Within three hours, the submarine is brought out of the water.
The submarine's skipper orders a diver to latch a mine onto the Ramona. But a twist of fate saves the Ramona. Gorgonzola is identified as Rastapopoulos and ordered to give up. But Rastapopoulos gives them the slip at the last instant.
Later, Tintin and Haddock return to Marlinspike. They meet Calculus and Nestor. Jolyon Wagg comes in with a pack of racing cars, telling them that a rally is about to take place at Marlinspike.