Two Scotland Yard detectives investigate the murder of a young woman of mixed race who had been passing for white. As they interview a spate of suspects -- including the girl's white boyfriend and his disapproving parents -- the detectives wade through a stubbornly entrenched sludge of racism and bigotry.

Few people know of the chilling reality behind the mysterious phenomenon of unidentified flying objects. Beings from a dying planet have arrived on Earth to kidnap humans and take over their vital organs. Against this threat, SHADO has been created, a secret organisation equipped with the most advanced technology and the best men.

When the union in his factory walks out on strike, a family man refuses to participate, risking the wrath — and retaliation — of his fellow workers.