In Brussels, Tintin and Captain Haddock bump into an old acquaintance, General Alcazar. Returning to Marlinspike Hall, they find that "another" acquaintance, the Emir of Khemed, Mohammed Ben Kalish Ezab, has been overthrown by his nemesis Sheikh Bab El Ehr, and that the Emir has accordingly sent his son, the disobedient Abdullah, to stay at Marlinspike for his own protection. The police detectives Thomson and Thompson visit, informing Tintin that Alcazar is seeking to purchase military aircraft from J. M. Dawson. After further investigation, Tintin discovers that Dawson has also sold military aircraft to Bab El Ehr. Realising that the only way to be rid of Abdullah is to restore the Emir's control of Khemed, Tintin, Haddock, and their dog Snowy travel to the Middle Eastern country. However, the trio narrowly survive a bomb planted aboard the plane to kill them as a result of Dawson discovering that Tintin spied on him, and are able to slip into the city of Wadeshah unobserved. There they meet an old friend, the Portuguese merchant Oliveira da Figueira, who helps them to escape the city and ride on horseback to the Emir's hideout. During the journey, they evade armoured cars and fighter planes ordered to intercept them by "Mull Pasha", who is actually Tintin's old nemesis, Dr. Müller.