You should not get involved in other people's marriage
Henry is at a restaurant when he sees two strangers Mary and Don arguing about Don's infidelity.
Henry wants to say something to the couple.
Henry tells the couple that he can hear them and that this is not really a conversation for a public place.
Henry tells the couple that they're crazy for staying together and tells Mary in particular to leave Don.
Both Mary and Don are happy that Henry pointed out how loud they are before they embarrass themselves further.
Both Mary and Don are angry Henry was listening and are annoyed he thinks he can provide his input into their private life.