Bob Morane

Ylang Ylang has discovered a substance in a volcanic crater that, when it comes into contact with water, produces a gas that causes people to suffer severe hallucinations. The head of the SMOG crime syndicate plans to use the gas during a speech by the American president in New York. Since people would see prehistoric creatures through the gas, she could calmly kidnap the statesman in the panic that breaks out and then blackmail the country. Bob Morane sees through the situation and tries to prevent Ylang Ylang's plan.