The One Thousand: Book Two: Team of Seven

It is the late 1960s... A team composed of humans and benevolent aliens hunt for murderous, alien-possessed convicts with enhanced powers who have escaped from prison. They discover that this fellowship of psychopaths is preparing an elaborate party for hippies and other street people in a remote mansion built to simulate a Medieval castle, and that they are planning to slaughter everyone who attends. Now the seven are faced with the task of locating the mansion and stopping the killers...