On a beautiful June day in 1965, a dozen girls-classmates at a picturesque Blue Ridge women's college-launched their homemade raft (inspired by Huck Finn's) on a trip down the Mississippi. It's Girls A-Go-Go Down the Mississippi read the headline in the Paducah, Kentucky, paper. Thirty-five years later, four of those "girls" reunite to cruise the river again. This time it's on the luxury steamboat, The Belle of Natchez, and there's no publicity. This...