She was in labour, which is why they were rushing into town. She died giving birth while he was gone, and the stranger is his newborn child.
Everyone pictures the stranger as a grown man.
A husband and wife are speeding into town when their car runs out of petrol. He makes sure she locks the doors and keeps the windows shut, then walks off for help. When he gets back, the doors are still locked and the windows still shut, but his wife is dead and there’s a stranger in the car with her. What happened?
Give me a hintThe hint
Why were they in such a hurry?
Reveal the answerHide the answer
She gave birth, and the stranger is the baby
Source: Agnes Rogers, How Come?, 1953, via Jed Hartman’s list of situation puzzles, no. 1.82