As a cyclone ravages Mexico City, Dr Keel and Dr Sandoval struggle to help the victims. The suffering is intensified becuase some donated cooking oil is revealed to be hydraulic fluid in the wrong tins. The two doctors track down the history of the cans via a trader in Marseilles and discover that a financier named Zeebrugge was responsible for the deception. Dr Sandoval tries to kill the financier, but Keel prefers to make an arrest.