Romeo and Juliet are playing a 4-player game of Dominion. Romeo has spotted a complicated forced-win for Juliet and desperately wants to tell her, but he remains silent as he shouldn't upset the other players.
Using only the gameplay of Dominion, how can Romeo send a message to Juliet?
So.. is the puzzle how can Romeo tell Juliet something (i.e. give her information) without giving any information to the other players? And it's Juliet's turn? If I'm understanding this correctly...
During Juliet's turn, she has played some number of Torturers so that the other players (players A and B) don't have any cards in hand, but Romeo was unaffected because of
Moat . Juliet then starts Thrown-Rooming some Masquerades so that the players pass cards in a circle. Every card that players A or B receive must then be passed along upon next Masquerade. If Juliet passes that same card to Romeo that she had received prior, that's a 0; passes a different card, that's a 1. They continue to communicate via binary until some sort of message is fully constructed. However, because player A doesn't know what was passed from Juliet to Romeo (through player B), or vice-versa for player B, neither of A nor B are able to know any of the bits.
EDIT: This allows for 2-way communication. If all you want is 1-way, and Juliet is directly on Romeo's left, then the solution is easy -- just use Masquerade to pass bits.