In Cigars of the Pharaoh, Tintin pursued an international group of drug distributors through the Middle and Far East. He managed to catch them all, except for the leader, who fell down a ravine. His body was not found. In order to unravel more of the network and stop the opium production at the source, Tintin travels to Shanghai, a major city-port in China, where he is eagerly awaited by the assassins of the opium consortium.
However, the attempts on Tintin''s life are foiled by a young Chinese man who is later struck by Rajaijah juice, the poison of madness, used by the opium gang.
While in Shanghai, Tintin meets Mitsuhirato, a Japanese businessman, who urges him to return to India and protect his friend the Maharajah.
Tintin also helps a young Chinese boy against a racist bully Gibbons, a friend of Dawson, the corrupt police chief of the Shanghai International Settlement. Gibbons and Dawson set about making life difficult for the young man.
Tintin is on his way back to India by ship when he is kidnapped and taken ashore. He wakes up in the home of Wang Chen-Yee, the leader of a brotherhood called "The Sons of the Dragon" dedicated to the fight against opium. Wang''s son is the young man who helped save him on two occasions but is now insane. He goes about threatening to cut people''s heads off with a sword (thinking it will "show them the way") and only his father''s stern authority can keep him in check.
Wang also reveals that Mitsuhirato is a major villain: a Japanese secret agent and drug smuggler. Tintin follows Mitsuhirato and sees him blowing up a railway line (this is based on the real-life Mukden Incident). No one is killed and damage is minor, but it is blown up into a major Chinese terrorist incident and used as a pretext for a Japanese invasion of Manchuria.
Having obtained a sample of the poison of madness, Tintin tries to make contact with Doctor Fan Se-Yeng, an expert of insanity, who he thinks will cure Wang''s son. However, Doctor Fan has been kidnapped by the opium gang, presumably to prevent him from doing this.
Tintin rides a train to Hukow, but a flood washes the tracks, and all the passengers must disembark. He rescues a young boy from drowning, Chang Chong-Chen. They become fast friends, and Chang rescues Tintin from the Thompsons who had reluctantly arrested him under orders.
Wang and his family are kidnapped by Mitsuhirato. In order to find them, Tintin hides in one of the barrels on an opium ship. But it turns out that he was seen, and when he emerges he is confronted by Mitsuhirato armed with a gun. Then the boss of the opium cartel is revealed to be Rastapopoulos (see Cigars of the Pharaoh for back story). Tintin is incredulous that this man he thought was a friend could be the gang leader until Rastapopoulos reveals on the tattoo of Kih-Osk on his forearm. However, the The Sons of the Dragon had previously overpowered Mitsuhirato''s thugs and had hidden in the other barrels, revealed themselves, shot the gun out of a crook''s hand, had guns pointed at all the other crooks, who had to surrender.