Question: What exactly did Jonathan and Maddie give to the tramp in exchange for information?
Answer: It was actually mouthwash.
Plot hole: Why on earth would a sleazeball like Adam Klaus be worried about news of a one-night stand being revealed? He'd welcome the publicity, if anything. Anyone threatening to go to the papers with news of a bit of rumpy-pumpy with him would be wasting their time.
Madeline Magellan: Enough with the pedanticism and let us eat.
Jonathan Creek: The word is pedantry.
Chosen answer: It was a bottle of turpentine.
Methylated spirit, always coloured purple.