Others include "Young and Innocent", "Saboteur", "Spellbound", "Stage Fright", "Strangers on a Train", "I Confess", "To Catch a Thief", "The Wrong Man", "North by Northwest", and finally "Frenzy". "Saboteur" starts Robert Cummings as Barry Kane, a wartime aircraft plant worker during wartime accused of murdering his co-worker and best friend during an act of sabotage on the plant. He meets up with model Patricia Martin, played by actress Priscilla Lane, during his run from the law, and later, of course, the various Nazi/Fascist sympathizers along the way.
"Saboteur" is mainly like "The 39 Steps", even including similar plot devices such as handcuffs, the blonde who doesn't trust the main character in the beginning, a race across the country (in one case London to Scotland, and in the other California to New York), and meeting the "colorful" locals along the way. And so, just like "The Man Who Knew Too Much", I believe this is an American remake of one of Hitchcock's earlier works.
I think Robert Cummings was chosen because he comes across as a very ordinary American, sort of an "everyman" with whom the audience can identify. I like Priscilla Lane because her character is a more involved in the action than Madeline Carroll in "The 39 Steps" and Ruth Roman in "Strangers on a Train". As mentioned elsewhere, though, Otto Kruger steals the show as the villain. I also liked Vaughan Glaser's performance as the blind uncle; his lines are great. There are some funny touches all along the way for some comic relief, such as road signs featuring Priscilla Lane's character on them, and circus sideshow performers, and the truck driver, Murray Alper. Contrary to other opinions here, there aren't too many characters who believe Barry Kane's innocence immediately.
There are some slow parts, mainly when the action first moves to New York, but it picks up quickly when the last planned act of the fifth columnists gets underway.
It's one of my favorite films from Hitchcock (I put it in my top 5), especially in these days of the new war on terrorism. I think it hits home.
It makes you think, "Could my coworker be involved in something evil?" In fact, one of the movie posters for "Saboteur" proclaimed "Watch Out for the Man behind your back!" Imagine how that played in the mind of adults during the Second World War.