Greatnan shame on you. You've just given away the secret of an episode I have sat patiently through (and by golly, you do need a bit of patience) only to miss the ending each time. It's clearly the one. !!**!!! I've only just discovered Midsummer and am enjoying it. Nothing to offend my sensibilities.
And some people eat light bulbs, so I've heard.... I remember reading a crime novel years ago where ground glass had been put into food.......and she died - of course!
I have been watching an episode of Midsomer Murders where a man is supposed to have been poisoned by ground glass. I looked it up, and apparently crushed glass could kill you eventually by cutting up internal organs, but you would know something was wrong and presumably seek help. And who would eat or drink anything with sharp bits in it? Ground glass, fine enough not to be noticed, would not harm you at all.