A "Cinderella Liberty" is Navy jargon for a pass that runs out at midnight. Sailor John Baggs, Jr. (James Caan) has such a pass, and intends to make the most of it while his ship is docked in Seattle. He "wins" prostitute Maggie (Marsha Mason) in a pool game, but backs off at a "wham-bam-thank you ma'am" when he finds out that Maggie has a son, an 11-year-old mulatto (Kirk Calloway) -- and that there's another baby on the way. John has so much empathy for Maggie's travails that he marries her. When she loses her baby, however, Maggie feels unable to resign herself to living with John, plagued by both guilt and an unwillingness to be tied down -- thus forcing John to fight for her. Darryl Ponicsan adapted his own novel.