at this time, lang and his wife thea von harbou were developing the film "m". von harbou and lang were friends with jacques since creating the first mabuse film "dr. mabuse the gambler", and they went on vacation with each other. lang asked jacques for help with the screenplay for "m" and asked for suggestions for a new mabuse project. jacques sent lang his unfinished work for "mabuse's colony". lang used the idea of mabuse's will from the story and began working on an outline to what would become "the testament of dr. mabuse".