The Hound of the Baskervilles (1959 movie)
Dr. Mortimer is never put in charge of watching over Sir Henry in the novel; therefore he is not considered negligent by Watson when Sir Henry ventures out onto the moor alone. Mortimer in the novel is an "amiable, unambitious, absent-minded" doctor in his late twenties. The film's version is much older and is made deliberatley unlikable from the start as a red herring.