The novel "Stranger At Home" by George Sanders, which this film is based on, was actually ghost-written by Leigh Brackett. An unrelated novel also credited to Sanders, "Crime On My Hands", features Sanders as an amateur detective, similar to his "Saint" and "Falcon" characters. That novel was ghost-written by Craig Rice, who wrote two of the "Falcon" films.
Correcting the above
Tom Conway was George's brother and did play the Falcon, however George played the part first and was replaced by Tom.
Tom NEVER played the Saint.