Wyndham, John. "Random Quest"
Divergence: 1926 CE
What if: Some event in the mid-1920s resulted in no World War II and the continuing existence of the League of Nations.
Summary: In 1954, a scientist is knocked sidewise into another world and then after several weeks snaps back. He embarks on a search to find this world's analog of a woman with whom he fell in love in the other.
Comments: Allohistorical development is fairly small, although definitely present. The story is the ~Basis for the 1971 theatrical movie Quest for Love, starring Joan Collins and Tom Bell, and for the 2006 BBC4 movie titled Random Quest starring Samuel West. Also done as an episode of "Out of the Unknown" for BBC2 in 1969.
Published: In The Infinite Moment, Ballantine 1961; Consider Her Ways & Others, M. Joseph 1961 (0718100662), Penguin 1965 (0140022317BUY); The Vintage Anthology of Science Fantasy (ed. Christopher Cerf), Vintage 1966; and As Tomorrow Becomes Today (ed. Charles W. Sullivan), Prentice-Hall 1974 (0130500399, 0130500216).