What makes Armand realize that Dussault is not involved in the attempt on Stephen’s life in the novel, All the Devils Are Here?

Dussault threw Honore's nickels in the fountain when Armand was looking so that they would both know where they were. It is at this point that Armand realizes that Dussault is not involved in the attempt on Stephen’s life because he saved Daniel by not turning the coins over to Girard.