The Sign of Four streaming: where to watch online?
Currently you are able to watch "The Sign of Four" streaming on Amazon Prime Video, Amazon Prime Video with Ads or for free with ads on The Roku Channel, Fandango at Home Free, Filmzie. It is also possible to rent "The Sign of Four" on Amazon Video, Fandango At Home online and to download it on Amazon Video, Fandango At Home.
Besides streaming, you can also buy the movie on DVD from Amazon DVD / Blu-ray and on Blu-ray from Zavvi, Amazon DVD / Blu-ray.
You can also stream the title for free on Plex, Plex Player, Plex Channel, Fawesome.