In his interview with François Truffaut on "Shadow" (first published in 1967), Alfred Hitchcock said the dense, black smoke belching from the train that brings Charles Oakley to Santa Rosa was a deliberate symbol of imminent evil.
Edna May Wonacott, who plays young Ann Newton, and Estelle Jewell, who plays Charlie's friend, Catherine, were both locals of Santa Rosa, where the film was shot on location. Many of the film's extras were also locals of the town, which was too far away from Hollywood to be affected by Actors Guild guidelines demanding the use of professional actors.
Uncle Charlie is connected to all three children (Young Charlie, Ann, and Roger) in the family. Uncle Charlie is closest to Young Charlie. Like Ann, Uncle Charlie was always reading when he was young. Like Roger, Uncle Charlie is the youngest in the family.
The trivia items below may give away important plot points.
There are several vampire references throughout the film, including: - Jack Graham asks Ann to tell Catherine the story of Dracula. - Uncle Charlie comes from Philadelphia, "Pennsylvania." Dracula comes from "Transylvania." - Uncle Charlie's line 'The same blood runs through our veins' is from the 1931 film Dracula, were Dracula says the exact same line in reference to Mina when he and Van Helsing have their "battle of wills" to prove he now has power over her. - Telephathic communication between Young Charlie and Uncle Charlie is also connected to the relationship between Mina Harker and Dracula. - Uncle Charlie is also killed on the train "returning" to the east, much like how Dracula dies returning to the east. - As the landlady lowers the blind and the light disappears from his face, Uncle Charlie rises. This image is also interesting to note, as the blinds are traditionally drawn where there is a dead man in the room.
Hitchcock puts lots of personal elements in this film. For Example, Alfred Hitchcock's middle name is Joseph. Young Charlie's father's name is "Joseph" Newton. Like Roger, Alfred Hitchcock was the third and youngest child in the family. Alfred Hitchcock's mother name was Emma Hitchcock. Young Charlie's mother's name is Emma Newton. Uncle Charlie's bicycle accident in the film happened to Hitchcock when he was young. Ann Newton reads the book "Ivanhoe" in the beginning of the film. Alfred Hitchcock knew the story of Ivanhoe by heart when he was young. Young Charlie drives the car in the family. Alfred Hitchcock's wife Alma Reville loved driving. Like Alfred Hitchcock, Herbie Hawkins (played by Hume Cronyn) is obsessed about the subject of the murder and he is also mother dominated.
In Hitchcock/Truffaut "audio" interview, Hitchcock said this was his favorite film. In Hitchcock/Truffaut "audio" interview, Truffaut discusses with Hitchcock about the use of "two" in this film. Two Charlies (Uncle Charlie and Young Charlie), Two scenes at the railway station (the arrival of uncle charlie and the leaving of Uncle Charlie), Two men on the run (One man in the east and Uncle Charlie in the west), Two men on the run are killed (one by the plane and other by the train), Two policemen, and the two visits of police into the house.
Alfred Hitchcock used the idea of "You destroy the thing you love" in this film. In Peter Bogdanovich/Hitchcock Interview, Alfred Hitchcock mentions the idea of "You destroy the thing you love" through Oscar Wilde. Young Charlie loved Uncle Charlie. But she ended up destroying him at the end of the film. In Truffaut/Hitchcock Interview, Hitchcock mentions that it is implied at the ending (Young Charlie with Jack Graham in front of church) that Young Charlie will be in love with her Uncle Charlie for the rest of her life.
Other vampire references: When the audience is first introduced to Uncle Charlie, he is lying on his bed, arms folded across his chest, suggestive of a vampire lying in his coffin. Uncle Charlie remains unseen on the train (traveling to Santa Rosa) is a lot like Dracula's trip from Transylvania to London. Unlike Dracula who drains the blood from a living being, Uncle Charlie corrupts the minds of the young ones by taking their innocence from them.