The Blue Lotus: Part 1 - S1-E8
Plot hole: When the Chinese man who visits Tintin goes crazy from the same type of dart that was shot at Doctor Sarcophagus, he tells the guard to go to the Maharajah's son. About 9 seconds later, they are seen bringing the boy back inside. There wouldn't have been enough time for them to get all the way to the ground considering they were a floor above them a few seconds ago. (00:03:05)
Chosen answer: It is a pill that makes alcohol taste disgusting.