The United States Air Force has lost a plane carrying a hydrogen bomb over the Adriatic Sea between Italy and Yugoslavia.
Yugoslavia claims it has located the bomb in deep water off Venice and intends to use it to blackmail Italy into giving up sovereignty of Trieste which is currently administered by the United Nations following World War II.
AXE suspects that the head of Yugoslav Intelligence, Vanni Manfrinto, knows the exact location of the bomb and has the ability to arm it underwater.
Manfrinto's only vice is women and AXE have arranged for one of their operatives, Princess Morgan de Verizone – an international prostitute – to meet up with him.
Carter (in disguise as American businessman, Robert Corning) and Princess de Verizone meet up on the Orient Express en route from Paris to Venice and spend the night together.
The princess takes up Manfrinto's open invitation for her to return the next evening giving Carter a new opportunity to infiltrate his organization and eliminate him.
Carter kills the divers and disables the support vessel and then swims back to the casino on the Lido.
Just as he is about to torture Manfrinto into revealing the exact location of the bomb, Hawk enters and relieves Carter of his duties.