Ivan Nikitich Sokolov, attache to the Soviet embassy in London, opened the airport locker and withdrew an envelope. He glanced at it briefly, tucked it into his diplomatic pouch, and turned to go. At that moment, two men descended on him. One was dark and muscular, the other slighter with curly hair, but they both wore the same resolute expressions. As they seized him, an older man with thinning blond hair came up. "Mr Sokolov, you have no idea how long I've wanted to do this." He took the diplomatic pouch and opened it.

Sokolov blustered, "You cannot! I have diplomatic immunity!"

The blond man smiled thinly. "Perhaps I should introduce myself. I am Major George Cowley of CI5, an agency answerable only to the Home Secretary, and I don't even need a warrant." He opened the envelope and took out a sheaf of mechanical drawings. "I don't have the expertise to evaluate this but I'm sure the Second Sea Lord will be happy to enlighten me."

The Russian wilted. "I am only a courier."

"I know." Cowley slid the papers back in the envelope. "We're interested in who got the plans for you."

"That I do not know. I go regularly back and forth to Soviet Union and I check the locker every time I leave this country. If there is something for me, I take it. It is, how do you call it, a dead drop." Sokolov smiled. "What I do not know, I cannot betray, da?"

"Da." Cowley sighed. "I can't charge you with espionage." He waited for Sokolov to look triumphant, then went on. "What I can do is deport you. Bodie, Doyle, see this gentleman gets on the plane."

They dragged the Russian away. Cowley watched until they were out of sight in the boarding bridge, then went to a phone. By the time Bodie and Doyle returned, he had finished his call. "Any problems?"

"Some weeping and wailing about how he would be shot as soon as he got off the plane in Moscow." Bodie grinned wolfishly. "I don't consider that a problem."

"Neither do I," said Cowley. "Well, come along. The Second Sea Lord is anxious to meet with us."

Admiral Frederick Burney was a tubby man with a round face and a big smile, and as he came around his desk to shake hands with Cowley and his subordinates, all three found themselves pondering how often the iron men of this world rarely looked the part outside of the cinema.

Burney sat behind his desk and his beaming face became very serious. "Mr Cowley, I wanted to meet with you so I could personally emphasize the seriousness of this situation. As you know, one of my responsibilities is managing the building of submarines. My office is currently working on a new submarine, the Resolution class, and some information about the vessel's speed and range has turned up in Moscow. I certainly don't want such items to be common knowledge in Russia, but they are not critical to our national security." The Second Sea Lord took a deep breath. "Specs of the armament, on the other hand, must not be allowed to fall into enemy hands. The Resolution class submarine will carry up to 16 UGM-27 Polaris A-3 missiles. The Polaris has a range of 2500 nautical miles; three thermonuclear warheads each yielding 200 kilotons; an inertial guidance system and fire control; and a re-entry vehicle. It is a formidable weapon and the safety of our country will be compromised if the Russians get it."

"Admiral, with all due respect, I think this is a job for the Ministry of Defence," said Cowley.

"The Ministry of Defence!" Admiral Burney snorted. "The Ministry of Defence investigated when the first document about the speed of the submarine was smuggled into Russia. They were still trying to get their thumbs out when information about the range turned up in Moscow." He rattled the papers Cowley had taken from Sokolov. "This is a plan of the propulsion system. I have no confidence in the Ministry of Defence. I do have confidence in the Home Secretary, and he says you are the man for the job."

"Just who has access to this information?" asked Bodie.

"Myself, of course," said the Second Sea Lord, "but I hope I am not a suspect. I would hardly have called the Home Secretary if I were guilty."

Cowley chuckled. "Highly unlikely. Who else can you suggest?"

Burney said thoughtfully, "There is my personal assistant, Thomas Watkins, but he's been with me for years. I really can't picture him doing such a thing." He spread his hands. "I don't know who it could be. That's your job, man!"

"Yes, of course," said Cowley. "We'll just have to start from scratch, but we will be paying special attention to Mr Watkins. You may think him above suspicion, but there are quite a few former British subjects who were above suspicion once and are now living in Moscow."