Superman -- The Mystery Of The Letter-Part 3

The Man of Steel takes flight in this 1948 serial chapter of The Adventures of Superman. Lois Lane's sister Diana is back from Europe with a mysterious letter -- and a masked villain will kill to get it. With both Lane sisters held captive, Superman must race across Metropolis to break the case wide open. Bud Collyer stars as Superman/Clark Kent in part three of a Cold War-tinged spy thriller.