Samuel Langhorne Clemens and Dorothy Quick met aboard the S. S. Minnetonka in 1907. He was seventy-two years old, she almost eleven. The two began a great friendship that would endure until his death some years later. Dorothy became a frequent houseguest of Twain's, both at his Tuxedo Park home, in New York City, and in Redding Connecticut. Her recollections of life in those places dispel the image of Twain as a man bitter and pessimistic in his later...