Dr. Lily Houghton enlists the aid of wisecracking skipper Frank Wolff to take her down the Amazon in his dilapidated boat. Together, they search for an ancient tree that holds the power to heal – a discovery that will change the future of medicine. It tells the alternate history of the captain of a small riverboat who takes a scientist and her brother through a jungle in search of the Tree of Life. In 1916 London, McGregor Houghton presents his sister Dr. Lily Houghton's "Tears of the Moon" research to the Royal Society, which bars women members.