The Assassination Bureau has existed for decades (perhaps centuries) until Diana Rigg begins to investigate it. The high moral standing of the Bureau (only killing those who deserve it) is called into question by her. She puts out a contract for the Bureau to assassinate its leader on the eve of World War I.
In turn-of-the-century England, Sonya Winter decides to invade the male-dominated world of journalism by proving that a series of murders are the work of a single organization. Once she has persuaded a wealthy newspaper proprietor, Lord Bostwick, to back her venture, Sonya poses as a prospective client and makes contact with the organization's chairman, Ivan Dragomiloff. She learns from him that the Assassination Bureau was founded by Ivan's father for the purpose of eliminating people who deserve to die. After offering £20,000 to dispose of a suitable candidate, Sonya startles Ivan by telling him that he is the man she wants assassinated. Admitting that the bureau has become motivated more by greed than by its original ideals, Ivan accepts the assignment. He assembles the bureau's members, including Lord Bostwick, and informs them that since they all deserve to die he will try to kill them before they can kill him. Lord Bostwick, who dreams of using the bureau to control the world, offers a £10,000 bonus to the successful assassin, but Ivan travels to the Continent with Sonya and uses every conceivable means to outmaneuver and destroy his opponents. By the time they reach Venice, Sonya has fallen in love with Ivan, and she aids him in duping the bureau into believing that he has been poisoned by the widow of Cesare Spado, Bostwick's trusted assistant. Inflated with confidence, Bostwick plots with the German bureau member, General von Pinck, to drop a bomb from a zeppelin on a castle where the kings and queens of Europe have assembled for a peace conference. But Ivan climbs aboard the zeppelin as it departs and corners Bostwick and von Pinck. When Bostwick fires his gun, the zeppelin catches fire and plunges to earth as Ivan alone manages to escape. A grateful Europe decorates Ivan for his gallantry, and Sonya is on hand to offer him her love.
