Hal Clement 
Needle [EPUB ebook] 
Needle Book 1

Two ships race in from outer space and crash in the Pacific Ocean. One contains a hunter, entrusted with a vital mission. The other, his quarry – corrupt, evil, a criminal from an unearthly civilisation light years away. Yet both these creatures had one thing in common – they were unable to exist alone. Each needed a host, a human body they could invade and control.