On a hot August day, Harry Friberg gets an urgent assignment: to photograph United Air's shining new floatplane at the Lindarängen air harbor in Stockholm. The evening's crayfish party to celebrate the acquisition turns out uniquely unpleasant - and when the manger totals his car, and the chief pilot crashes into the sea after take-off, Harry realizes that a horrible crime has been committed, and it's time to call police commissioner Vesper Johnson.