Why Does Herr R. Run Amok?

The story

Technical draftsman Herr R. is a dependable guy. He gets along with his colleagues although his boss wants him to go beyond technical cleanliness to problem solving. He's a dutiful husband; his wife's a social climber and pressures him to seek a promotion, but they also share sweet moments. He's a caring father, helping his son with homework. His parents visit; his mother criticizes his wife. Old schoolmates drop by, as do neighbours. Some comment on his wife's expensive tastes. His promotion may be a long shot, especially after he gives a dull and tipsy toast at an office dinner. But why would Herr R. run amok?