Staying at the palace of the Maharaja of Gaipajama in India, Tintin is approached by a visitor from Shanghai in China. The visitor supplies him with the name of Mitsuhirato, a Japanese businessman based in Shanghai, but before finishing his message is hit by a dart dipped in Rajaijah, the "poison of madness". Tintin and his fox terrier Snowy travel to Shanghai to meet Mitsuhirato, who warns them that the Maharajah is in danger and that they should return to India. Surviving several attempts on his life by mysterious assailants, Tintin attempts to leave for India by boat, but is kidnapped. His abductors reveal themselves as members of a secret society known as the Sons of the Dragon, who are devoted to combating the opium trade. Their leader, Wang Chen-Yee, explains to Tintin that Mitsuhirato is both a Japanese spy and an opium smuggler, and enlists Tintin in their fight to stop him. Tintin agrees, and spies on Mitsuhirato at the Blue Lotus opium den. Following the spy, he discovers him blowing up a Chinese railway. The Japanese government uses this as an excuse to invade Northern China, taking Shanghai under its control.