What “game of cards” is Sydney playing with Barsad? (From Book 3 Chapters 6-10)

Carton acts as a deus ex machina (a god-like intervention), arriving on the scene and instantly working to save Darnay's life. As we can see, he is a changed man. He longer hides from the world in liquor; instead, he uses it to find all sorts of information about the world. He no longer tolerates being spoken at; he loudly and forcefully orders Barsad around. Finally, he no longer speaks as a wastrel, but as a man with a purpose. He uses the last vestiges of his old life to provide information for his purpose through likening his questioning to the rake's game of cards.

Carton lays the information (cards) on the table and produces the possible results. The question would be if Barsard is willing to make a gamble against his own life.