Filmed in the late '40s I think. Kind of a noir-type movie.
A naive “spinster” schoolteacher from San Diego (I think) is on holiday in Mexico where she meets a suave and debonair (European?) gentleman who sweeps her off her feet. They marry after a whirlwind courtship and take off to drive through Mexico on their honeymoon. As I recall, his real aim is to snag a Green Card, and the “romance” does not end well.
The stranger, if not Charles Boyer himself, was definitely of that type.