 Some unknown maniac is threatening a navigation company to blow up one of its luxury transatlantics, the "Britannic", now in high sea with 1200 passengers. He is asking for a £500,000 ransom, otherwise the 7 bombs aboard will explode. An experienced anti-bomb squad is sent to the "Britannic", but although all the bombs are located, a very high skill level will be necessary to dismantle them. Perhaps that task is impossible...