Rowers in the 1936 Olympics, English twins—both known as J.L. Sawyer—have very different experiences in World War II. One joins the RAF, and is shot down after a bombing raid, later becoming Churchill's aide-de-camp. His brother works with the Red Cross, rescuing bombing victims in London. In this ingenious 2003 winner of the Arthur C. Clarke Award, however, one brother lives in the world we know, and the other inhabits a different reality in which the war ends in 1941—while a baffled historian attempts to piece together the truth.