What happened with phineus and mr prude

One of the school masters, Mr. Prud'homme, noticed the boys' absence from dinner the previous evening, and pays them a visit to discuss the offense. Finny (aka Phineas) concocts some long-winded but amusing excuse about going swimming, watching the sunset, etc., and how the activities were absolutely necessary in light of their almost being of age for the draft; Mr. Prud'homme is won over by Finny's charm in trying to weasel his way out of trouble, and the master forgets any charges.