A chance discovery leads American mining engineer Ben Harris and acquaintance Harold to discover a lost city under the sea while searching for their kidnapped friend Jill. Held captive in the underwater city by the tyrannical Captain (Vincent Price), and his crew of former smugglers, the three plot to escape...

England, 1645. The cruel civil war between Royalists and Parliamentarians that is ravaging the country causes an era of chaos and legal arbitrariness that allows unscrupulous men to profit by exploiting the absurd superstitions of the peasants; like Matthew Hopkins, a monster disguised as a man who wanders from town to town offering his services as a witch hunter.