The long-running blood feud between two alien peoples came to a sudden close a century ago when both races colonised the planet Sigma IV. But their unaccustomed harmony turns out to be caused by a natural gas released by their new home planet - an effect that scientists now determine will kill them over time. A treatment intended to nullify the long-term damage and danger has catastrophic results, triggering worldwide carnage as long suppressed aggression and rage are suddenly released. In the