too many people face near death with an unknown poison, fired mysteriously by a dart. the police cannot fathom how the darts are being fire. no traces are left by the perpetrator. Private detectives are also confused. The main clue is an email sent each time by the perpetrator referring to the unacceptable number of deaths each year from traffic pollution and demanding action. If no action, another dart will follow, and with each dart death is that much nearer. There is much tension at several points, until it builds to a very exciting (and surprising) climax.