Unsatisfactory ending (SPOILER)
The rad hose blowing again was a bit of a weak final sting. It would have been better if Grace after pushing Bobby over the canyon, she was to take off with his car and money only to be stopped round the next bend by the gang leader and a bullet promptly put in her head. He takes the money and drives off. The End.
Of course he would have to be written into the screenplay more, perhaps doing some detective work, gradually catching up, entering the husbands house seeing the scene of violence and noticing the open safe.