The original story, before Andrew Lloyd-Webber americanised it (and ruined it, IMO), was written by Hayley Mills' mother, Mary Hayley Bell, and starred Hayley as a Northern girl who thinks she finds Jesus Christ returned to Earth and living in her father's barn. In fact the man is a convict on the run (beautifully played by Alan Bates, one of his best early roles).
The girl and her sister and little brother (Alan Barnes, a superb performance) cosset the man and plot to keep him secret from the adults, because of what happened to him 'last time'. The man in turn is bewildered by the increasing adultation and attention of the neighbouring kids.
One of the strongest points of the story, aside from the contention that religion really couldn't cope with the return of Christ, is the developing attraction between the pre-teen Mills and Bates. This is understated but unmistakable, and owes a lot to Hayley's talent when she was a child actress. The music by Matthew Arnold is superb and Bryan Forbes' direction is sympathetic and cleverly done.
Perhaps the final symbolism is overdone but 'Whistle' is an excellent film that lingers long in the memory.