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Originally released in England in 1941 as This Man is Dangerous, The Patient Vanishes was distributed in the US in 1947 to capitalize on the burgeoning popularity of James Mason. The story concerns the friendly rivalry between private detective Mick Cardby (Mason) and his father, Scotland Yard inspector Cardby (Gordon McLeod). Both father and son work shoulder to shoulder to rescue the kidnapped daughter (Barbara James) of a wealthy industrialist. In "Bulldog Drummond" fashion, the girl had been abducted while a patient at a somewhat shady hospital, leading the detectives to interrogate several suspicious-looking medical types. What romance there is can be found in the bantering relationship between Mick Cardby and his secretary Mollie (Margaret Vyner). Though no evidence exists to support this theory, it's possible that The Patient Vanishes had been intended as the first in a series of "Ellery Queen"-style mysteries starring Mason and McLeod.