How is Don John and his companions plot foiled?

 Borachio basically admits everything to Don Pedro and Claudio. They both feel badly about slandering Leonato. Leonato forgives them. Both will mourn Hero in public and clear her name. Claudio gets a pass for being a knucklehead over hero: guys can be impulsive in matters of the heart. All is well. Don John and his accomplices run away but are caught to face justice.