Speakeasy

Clue projected onto The National Gallery, London.

<spoiler> Use the left-side pattern in the London event to spell out the letters on the napkin. The central pattern spells "steel wheel". The outer pattern spells out "A Golf Bag, Slot Machine, Three Wise Men." These four terms are slang for poker hands. Three Wise men is 3 kings, Slot Machine is 3 sevens, golf bag is a club flush and steel wheel is a straight flush. The winning hand and thus the answer is straight flush.

</spoiler>

Next book: Pirate Treasure