In Dawn Patrol, Otto Kleiner was the owner of a posh restaurant night-club in Mayfair as well as the Listern Flying Club in Sussex. As Gaskin told Biggles, Otto was the kind of person the police would like to know more about. Although his restaurant kept proper books, his lifestyle did not seem to tally with what he declared to the taxman. His restaurant was also known to be the hang-out of several known drug addicts. When Ginger spotted Otto's son, David Kleiner flying suspiciously in an aircraft with false registration markings, Biggles began to put two and two together and suspected an aviation connection possibly in the smuggling of illegal drugs. By observing David Kleiner's movements and that of his brother in Paris, Biggles was able to catch David landing in England from France with a container of heroin on board. Both David and his father Otto were handed long prison sentences by an English court.