In pursuit of the mystery surrounding the death of a sailor who investigate Thompson and Thomson, Herbert Dawes, related to what appears to be a can of crab Karaboudjan Tintin goes to the freighter, which is captured by a band of criminals hiding in cans crab with which opium traffic. Tintin escapes the cabin in which they have locked up, and gives the ship's captain, Haddock. Captain Haddock, completely drunk, has fallen victim to the machinations of his mate, Allan Thompson, and knows that his ship carrying opium. When he takes the side view of Tintin.
Tintin and Captain of the ship managed to escape in a boat. The captain under the influence of alcohol makes a bonfire of the oars of the boat. In addition, a seaplane sent by the ship tries to kill them. They manage to gain control of the aircraft but, again due to alcohol, the captain makes it crash in the Sahara desert. After walking through the desert are saved by Lieutenant Delcourt (commander of the French Foreign Legion) who provides a means of transport to the port in Morocco Bagghar fictional.
The wreck is believed Karaboudjan but the captain is recognized in the harbor and smugglers abducted. Tintin tries to free it with the help of Thompson and Thomson discovered the head of Omar ben Salaad smugglers and arrested the entire band.