While sightseeing in London, Sue and her brother Eddie accidentally fell behind a tour group. But they were not going to panic. It never occurred to them that the tour guide would take the troupe away, leaving them alone in the gloomy old tower where there used to be a prison. Sue and Eddie did not even imagine that they would find themselves locked in the tower - in pitch darkness, among blank stone walls. And that a strange man in black will pursue them... to kill them.