The Seven Crystal Balls: Part 2 - S3-E4
Character mistake: Tintin mentions that they passed a beige car on their way to the road block with four people inside. First, they did not pass this car. The car stopped at the road block, and after they were asked about the black sedan, they drove away. Tintin, Haddock and the detective then arrived at the road block in their car, coming in from a different lane. Second, the car that was stopped at the road block only had three people inside, not four. (00:32:20)
Chosen answer: It is a pill that makes alcohol taste disgusting.