That's what Burton and a handful of fellow adventurers are determined to discover as they construct a boat and set out in search of the river's source, thought to be millions of miles away. Although there are many hardships during the journey--including an encounter with the infamous Hermann Goring--Burton's resolve to complete his quest is strengthened by a visit from the Mysterious Stranger, a being who claims to be a renegade within the very group that created the Riverworld. The stranger tells Burton that he must make it to the river's headwaters, along with a dozen others the Stranger has selected, to help stop an evil experiment at the end of which humanity will simply be allowed to die. --Craig E. Engler