This one is a little tricky:
Sam and his new bride Samantha were racing down a country road towards the city. Suddenly, the car started sputtering and died. It turned out he was out of gas, so Sam decided to go for help. Before he left, he instructed Samantha to lock all doors and keep the windows rolled up. The car wasn't a convertable, and didn't have a skylight. Sam returned to the car finding his bride dead and a stranger in the car. Since the windows and doors were still locked and closed, and the car was undamaged, how did Samantha die? And who is the stranger?