Tintin takes the chance of crossing the Japanese lines to have the poison analyzed even though there is a price for his head with the Japanese. Tintin passes the Japanese line in disguise and comes to Professor Fang Hsi-ying's house. While waiting there for very long time he learns that the Professor left with a gentleman called Mr. Rastapopoulos. While looking for the Professor, Tintin comes to Mr. Gibbons, who takes him to Dawson and Dawson turns him over to Mitsuhirato. But with Mr. Wang's help Tintin escapes and goes to Hukow where the ransom is to be paid for Professor Fang. On his way, he saves a orphan boy called Chang from flood water. They become friends very quickly and journey to Hukow together. There a cameraman tries to kill Tintin and Chang saves him. Tintin learns from the cameraman that the ransom letter is a false letter to send police to the wrong trail. Next Tintin goes to Mitsuhirato's house and finds out that they are going to attack Mr. Wang.