When Huston got his long-gestating adaptation of “The Treasure of the Sierra Madre” underway, he wrote to the source novel’s author to let him know about the upcoming movie, and that a good portion of it would be shot in his adopted homeland. Very little was known about Traven, other than he wrote his novels in German and he had lived for many years in Mexico, which provided the backdrop for much of his fiction.

After a spell in New York directing a play, Huston returned to Hollywood to find a letter from Traven waiting for him. Over many pages, the writer gave suggestions on how Huston might shoot the film, including lighting, location, and sets. With filming set for early 1947, Huston wrote back requesting an interview. He received the elusive response (via John Huston: A Biography):

“I can guarantee nothing, but if you will come to the Hotel Reforma, in Mexico City, in early January, I will try to meet you there. I make no promises.”

Huston decided to give it a shot and flew down to the Mexican capital. He waited at the hotel, but there was no sign of Traven. Just as he was about to fly back, he was approached by a thin man identifying himself as Hal Croves, a translator from Acapulco. Traven was unable to make it, but a type-written note said that Croves was authorized to discuss his novel in every detail.

Hughes signed him up as a technical adviser and, when he returned with the cast and crew, Croves was raring to go, helping with translation and advising on gold panning techniques. Despite his enthusiasm, Croves was very wary of cameras, leading Huston to suspect that he was really the mysterious author himself.