Here today in the Black Museum of Scotland Yard is a can of weed killer a familiar object, every suburban house with a patch of garden uses it as eventually one tires of pulling up weeds and turns to a can weed killer. Spraying the weeds eliminates the back aches. But does the poison in weed killer diminish in time? A chemist will need to answer that question when a can of weed killer in an English village is used in a terrible crime.