In Hitchcock/Truffaut, the first question Francois Truffaut asks Alfred Hitchcock is whether "the incident at the police station" is true.
Hitchcock: Yes, it is. I must have been about four or five years old. My father sent me to the police station with a note. The chief of police read it and locked me in a cell for five or ten minutes, saying, "This is what we do to naughty boys."
Truffaut: Why were you being punished?
Hitchcock: I haven't the faintest idea.
They begin Chapter Two by discussing The Lodger, which the master himself calls "the first true 'Hitchcock movie.'" It is about a man mistakenly suspected of being Jack the Ripper. Truffaut identifies this as "the theme recurs in almost all of your later works: a man accused of a crime of which he's innocent."
The psychology is obvious. As a boy, Hitchcock was put in jail, a punishment he did not deserve. He spent his career mostly making movies about characters falsely accused, chased and punished.
But he did not seem to be repeating himself. Although this theme is present in The Thirty-Nine Steps, North by Northwest, Vertigo, Frenzy and many more, each film has its own personality. I never noticed how consistent this theme is, until I read about it in the Hitchcock/Truffaut interviews.