Dr. Syn is a fictional character created by author Russell Thorndike in the 1915 novel "Dr. Syn: A Tale of the Romney Marsh." He is depicted as a kind-hearted vicar by day and a masked outlaw known as the Scarecrow by night, who fights against injustice in the Romney Marsh area of England. The character gained popularity and has been adapted into various media, including films and television series. Notably, the 1963 Disney film "Dr. Syn, Alias the Scarecrow" brought the story to a wider audience, showcasing the dual life of Dr. Syn and his adventures.