A strange huge plant which has appeared suddenly in Sagami Lake sucks in all the water including a sailing boat and a man in it. Azuma, head of the Japanese Branch of Unicorn Organization, thinks that it must be Satan Rose, a space plant brought to the earth by Dr. Over. He sends Daisaku (Johnny Sokko) and Minami to the house of Yasui, an old authority on the plant. Meanwhile Over tells Red Cobra, new head of the Japanese Branch of the syndicate, to kill Yasui before he gives information about the plant to Unicorn members.