In New York, Peter Sis receives a letter from his father. "The Red Box is now yours," it says. The brief note worries him and pulls him back to Prague, where the contents of the red box explain the mystery of his father's long absence during the 1950s. Czechoslovakia was behind the iron curtain; Vladimir Sis, a documentary filmmaker of considerable talent, was drafted into the army and sent to China to teach filmmaking. He left his wife, daughter,...