the weed of crime bears bitter fruit

No good will come from criminal schemes. The Shadow was a very popular radio detective series that began in the early 1930s. Its hero, playboy Lamont Cranston, had “the power to cloud men's minds,” a form of hypnosis by which he appeared off to the side of where people thought he stood (contrary to popular belief, the Shadow did not make himself invisible). After the credits at the end of every episode, the Shadow intoned, “The weed of crime bears bitter fruit. Crime does not pay! The Shadow knows,” and then utter a sardonic laugh. Another famous Shadow-ism was “Who knows what evil lurks in the minds of men?—The Shadow knows!”