Prince Albert II of Monaco arrives for the screening of Alfred Hitchcock's film "To Catch A Thief " to pay tribute to late Princess Grace in Monte Carlo September 15, 2012. [Photo/Agencies]

The earliest known surviving feature in which Alfred Hitchcock is credited was released online on Thursday after sitting under the noses of archivists for decades.

The recovered parts of 1924's "The White Shadow," in which Hitchcock served as an assistant director among other credits, will be streamed for free for the next two months at the US National Film Preservation Foundation's website, the nonprofit group said in a statement.

"The White Shadow," a silent British melodrama directed by Graham Cutts and a financial flop, tells the story of twin sisters, one angelic and the other soulless. It stars Betty Compson as the twins.

The New Zealand Film Archive stumbled across three of the film's delicate nitrate reels in its collection last year. No other copies are known to exist.

The foundation, which supports film preservation in the United States, said it was able to stream the film online from cash donations and bandwidth donated by the online film service Fandor.

Hitchcock, who shot to international prominence with "The Man Who Knew Too Much" (1934) and "The 39 Steps" (1935), is additionally credited as writer, art director and editor.

"The White Shadow" is also believed to be the first surviving production that Hitchcock, then 24, worked on with Alma Reville, whom he married in 1926.

Part of Hitchcock's and Reville's life together has been dramatized in "Hitchcock," a Fox Searchlight film starring Anthony Hopkins as Hitchcock and Helen Mirren as Reville. The film is set to be released on November 23.

The British-born director's obsession with hand-picked star Tippi Hedren ("The Birds" and "Marnie") was documented in the last month's HBO drama "The Girl".

A collection of freshly discovered still photos from Hitchcock's lost silent film "The Mountain Eagle" (1926) is expected to fetch $25,000 at auction in Los Angeles next month.