Burke turns in his police badge to work as a secret agent for the Federal Government. In his first assignment, he travels to Switzerland to work with the local Swiss police to crack an international ring of gold smugglers. Red Chinese gold is being smuggled from Switzerland into Latin America. The leader of the smugglers is General Edrego Barata, once a Latin American dictator who stripped his country of its wealth. Burke poses as syndicate hit man Paul Schreiner, whom Barata has never met. The plan goes awry when the real Schreiner is released from jail and exposes Burke. Burke manages to ultimately kill Barata.

In a combination of ""Day of the Jackal"" and ""The Man Who Knew Too Much"", Burke is sent to Paris to lacate the missing son of an American diplomat. The boy disappeared shortly after someone murdered his father's girlfriend by pushing her off the Eiffel Tower. When Burke arrives, he finds himself involved in a bizarre plot to assassinate Charles de Gaulle that takes him across the French countryside.

Burke poses as a jewel thief and infiltrates a criminal syndicate planning to put New York City to sleep with gas introduced into all the steam mains. The crooks, Albert Indigo, Tucson the Cowboy, Charlie ""The Arm"" Segal, and Ziggy White, then plan to loot the entire city. With the finances for the plan suppied by foreign interests, the syndicate also intends to kill a few important, connected people. While planning takes place at the Villa Ruposa, ""Mr. I"" undergoes a senate hearing, after which he vows vengeance on Senator Burrows. With the aid of co-spy Ursula Prince, Burke learns about the entire operation, but a beautiful crook named Silkie kills Ursula so she can have Burke all to herself. Burke ultimately triumphs and gets word to the police, who wear gas masks to round up the gang.

In London, Burke investigates two murders. The victims, a German electronics expert and a Yugoslavian engineer, had one thing in common: they both died after telephoning a certain number. Burke uncovers an intricate plot involving a password that means instant death, tin mines that have poison gas in the ventilating system, and a new, deadly Soviet satellite. Behind it all is megalomaniac who plans to destroy all the top people in England and take over the nation. Burke saves the day, but not before the Russians conspire to lead him to the brink of disaster.

Burke is sent behind the Iron Curtain and must smuggle out a famous scientist who has developed an ultra-powerful nuclear device. Another agent, Tony Scott, is assigned to assist Burke, but is actually in a conspiracy to steal the new weapon and sell it. Once they get Dr. Crystal into Austria, Scott kidnaps him and hooks him up to his bomb, which will destroy Vienna withing 22 hours if 2 million dollars in uncut diamonds aren't paid. Burke gets the diamonds released to an Austrian official. However, he too is in on the plot. Claiming the diamonds are fake, the official accuses Burke of stealing the real gems, planning to blame the inevitable disaster on Burke and then kill him. Burke finally discovers a special code consisting of 12 numbers that must be given in order to defuse the bomb. 1937 is one known sequence of numbers in the code. The remaining 8 are discovered at the last minute....8523....6472.