Quest for Love (1971)

A scientist's demonstration takes a disastrous turn, catapulting him into an alternate reality where the Second World War never happened and humanity hasn't set foot in space. In this strange new world, he is a celebrated author rather than a scientist. Following a heartbreaking event in this dimension, he returns to his original life, driven by a desperate need to reunite with the woman he fell for in the alternate realm. Unbeknownst to her, her survival hinges on his quest to find her before it's too late.