FREE ACTING TERRAN ENVOY
Seetee is the most dangerous substance in the universe - bring it into contact with the most stable of normal material and it explodes with enormous energy and destruction.
When Captain Kennedy and his crew, the top men of F.A.T.E. - Free Acting Terran Envoys - accidentally brush against some Seetee they not only thank their lucky stars for their escape, but realise it signals an emergency of the highest order.
Because such a swarm as they have encountered could cause the destruction of an entire solar system. And thy have reason to believe it is directed at out Sun - including particularly the Earth!