Its about this guy who is trying to figure out what is causing 12 people to go blue and die in like, a couple of hours.
Its a bit of a mystery cause when they run through the things that could have caused it, they find none of the usual suspects. Water, air, bad food, dirty dishes aren't the culprits so he has to think logically and figure out what the 12 people did in common.
In the end it was:
SPOILER(highlight to view)
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The one salt shaker in a breakfast diner which had salt peter in it instead of real salt. The company that made the salt also made salt peter and the two must have been switched. It seemed that the salt peter deprives a red blood cell of oxygen and additionally, all 12 victims had alcohol which further deprived oxygen so in effect they were suffocating from the inside - hence, the blue skin.