In one of the prestigious restaurants during banquet speech a large company's director Palmgren is killed in front of dozen guests . Case is lead by Criminal Investigation Officer Pierre Monson with his assistants. Suspect can be easily intercepted if only miserably lazy police officers Kvant and Kristiansson instead of catching criminal would not argue with father of little 3 years old boy who yelled: "Police, police, mashed potatoes" when they ate hot dogs. Help comes from capital in form of the famous Commissioner Martin Beck, who discovers that murdered industrialist was involved in illegal activities and had many enemies. The case is linked as well with government's "higher ends".