when jay l. bixby and i wrote our original story , little did we know where it would lead or what would become of it in the hands of men of great imagination and superb artistry-saul david , the film 's producer ; richard fleischer , the director and inspired conjurer of fancy ; harry kleiner , who wrote the screenplay ; dale hennesy , the art director and an artist in his own right ; and the doctors and scientists who gave us so much of their time and their thinking .