The Secret of the Unicorn: Part 2 - S1-E4
Continuity mistake: Mr. Silk is showing Thomson and Thompson to the door whilst Tintin exits with the scrolls and Max Bird's diary. When Tintin exits Silk's room whilst saying "Mr. Silk who made the mistake, gentleman", Tintin is holding the scrolls and the wallet and nothing is sticking out of the wallet. Tintin then exits the room handing the wallet to the detectives, and there are suddenly papers sticking out of it. (00:42:45)