The unfinished Gainsborough Pictures film Number 13 was to have been legendary director Alfred Hitchcock's directorial debut. Filming took place in London, England, and the story is about poor residents with low-income of a place financed by The Peabody Trust to benefit the very poor residents of London. The only known people who were in the movie were Clare Greet and Ernest Thesiger, and it was written by Anita Ross, who claimed to have a professional association with equally legendary actor Charlie Chaplin.
Unfortunately, production had to stop for an unknown reason, thus resulting in the film being lost. Hitchcock rarely ever spoke about the film during his lifetime except for a few occasions, and when his biographer interviewed him on his early life during the 1920s. Any footage of the incomplete movie is highly sought-after by film collectors and historians, and the only material ever made public was a single photo of the set.
UPDATE 11/4/17: (unconfirmed) More photos of Number 13 Have surfaced online! (Figster58)
The First photo consists of Alfred Hitchcock, Clare Greet and Ernest Thesiger in a poor house. (possibly for a set piece)
The Second photo also consists of just Clare Greet, and Ernest Thesiger.
The Third Photo just has a close up of Ernest Thesiger with a top hat on him.
The Fourth and final photo again also Clare Greet, and Ernest Thesiger who appear to be looking at something in Ernests hand.