Random Quest

"Random Quest" is a science fiction short story, which is also a love story, by John Wyndham. It was included in his 1961 collection Consider Her Ways and Others. It has been dramatised three times, twice under its original name and once as "Quest for Love".

The frame story deals with the elderly Dr Harshom in Herefordshire – who has a very rare family name, all of whose bearers are in one way or another related and are in some contact with each other.

In the early 1950s, the Harshoms, scattered throughout England, are greatly mystified by the appearance of a young man named Colin Trafford, who systematically and persistently meets each and every one of them, asking of a young woman named Ottilie Harshom that none of the Harshoms ever heard of and who is evidently very important to him. Dr Harshom decides to talk to Trafford and understand what it is all about – and the story consists mainly of what Trafford eventually tells.

It turns out that Trafford is a physicist, and that he was involved in a laboratory experiment which went wrong, lost consciousness and woke up to find himself in a parallel universe.

The parallel universe is similar to ours but there was a divergence in late 1926 or early 1927. The point of divergence is not precisely identified, but seems to have had the effect of preventing or greatly diminishing the effects of the Wall Street Crash in 1929. Trafford discovers that in the parallel world, Adolf Hitler never came to power and World War II never happened. Some of the implications are that:

On a more personal level, Trafford finds himself in the body of his counterpart in the parallel universe. As the story unfolds, he meets some old friends who have different partners, and at one point is taken aback to meet someone whom he remembers as having been killed in the war. He also catches a glimpse of his former wife, who in the original timeline died after a year of what he calls "satisfactory marriage", and who in the alternate world is alive, accompanied by another man, and does not recognise him.

...
Wikipedia