The detonator was a tin-copper electrical device that relied on an increase in temperature to affect the expansion differential of the two metals: any temperature above 100 degrees Fahrenheit would cause contact and thereby detonate the bomb.

He walked down the street on the sidewalk opposite the apartment building and glanced casually in its direction. The Secret Service agents were watching him as they would watch any pedestrian abroad at ten past four in the morning.

Ahead of him a car was sliding among the lights of the intersection two blocks distant. Riva timed his turn to coincide with the bleat of the car’s horn as it came into the block.

The horn attracted the Secret Service agents’ attention. The chauffeur was standing under the awning watching the limousine but his head also turned toward the advancing Chevrolet. Riva stepped off the curb between two parked cars and stood there waiting for the Chevrolet to go past him so he could walk across the street. He made it look as if he were walking toward the building beyond the apartment house.

He heard the pneumatic hiss of the car as it grew closer and he took a step back to avoid the splash of snow. The car went by, doing about twenty-five; the agents’ heads swiveled, indicating their steady interest in it. Riva stepped out into the avenue, looked both ways and began to cross. His path was designed to take him past the back of the limousine toward the next building down.

The agents were dividing their attention between Riva and the receding Chevrolet when Harrison in the back seat of the Chevrolet began to shoot. He was shooting at the windows of Milton Luke’s apartment. His shots were not expected to do any damage; it was a very high angle. But they accomplished their purpose; the Secret Service agents got behind pillars and cars and began to blaze away at the Chevrolet.

Riva did what anybody would do. You’re a pedestrian in the middle of the open and suddenly guns start going off: you dive for cover.

The cover he chose was the shadow of the VIP limousine and as he rolled past its rear bumper his left arm snaked up underneath the rear of the car. It took only a second or two to locate an exhaust pipe. He snapped the magnetized bomb on top of the pipe, immediately beneath the gasoline tank, and kept right on rolling over against the curb. Now he was a few feet behind the limousine, not within reach of it, and the Secret Service agents could see him if they chose to look.

The Chevrolet was just disappearing around the corner with a wail of tires and the agents stopped shooting. Riva got to his feet and when the nearest agent swung to glare at him Riva said, “Jesus Christ Almighty. What in hell was that all about?”

4:20 A.M. EST Satterthwaite scraped a hand down across his chin. The stubble stung his palm.

Bleary faces along the length of the big table in The Salt Mine. Voices barking into telephones. Satterthwaite had FBI Director Clyde Shankland on the line. “It looks like a maximum effort they’re putting up. First Hollander’s lawn, then five Goddamned bombs in that one building, then a sniper shooting at Luke’s windows. God knows where else they’ll hit. Look, I want every man you’ve got. We’ve got to provide immediate protection for every VIP in Washington.”

Kaiser was tugging at his sleeve. Kaiser had a telephone cupped in his hand. “It’s for you. The President.”

Satterthwaite said to Shankland, “Get on it, Clyde,” and slammed down the phone and grabbed the other one from Kaiser. “Yes, Mr. President.”

4:23 A.M. EST The city was amok with crying sirens. Riva circled the block and got back into his car and reached for the walkie-talkie. “Copasetik?”

“Copasetik.”

“They’re on their toes. Let’s do the alternate.”

“Copasetik.”

The central area was getting too hot; they would skip the other targets and head for the outskirts.

The Secret Service men had questioned him for several minutes but Riva’s identification was in order and his story was plausible and they had bigger things to worry about than him.

He put the car in gear and headed up toward Senator Forrester’s house.

4:28 A.M. EST Special Agent Pickett slid into the front seat of the limousine to use the radio. His hand brushed the manila folder on the seat and when he pushed it aside the ID sheet came ajar and he was looking straight into the face of the man they had questioned less than ten minutes ago.

He picked up the ID sheet and stared at the photo and blurted into the microphone.

“This is Pickett. I’ve just seen your man Riva.”

4:31 A.M. EST DeFord and B. L. Hoyt marched into the war room and Hoyt said to Satterthwaite, “Listen, they may be pulling something in that apartment house. Those rifle shots could have been a diversion to distract our people’s attention while someone slipped into the building. We’d better get Milton Luke out of there.”

“And put him where?”

“The White House. It’s the best guarded place we’ve got.”

DeFord said, “I’ll arrange for a heavy escort. We’ll want motorcycles and squadrols.” He reached for a phone.

4:33 A.M. EST The two FBI agents reached Arizona Terrace and parked at the curb.

“That’s the Senator’s house.”

“All right. No point waking him up. Look, I’ll post myself in that open garage across the street. You stick here in the car. Anybody shows up, we’ll have them crossfired.”

“Okay.”

4:37 A.M. EST Riva parked at the mouth of Arizona Terrace and within moments the Chevrolet drew up alongside. Kavanagh at the wheel.

“Everything okay?”

“So far,” Riva said.

“You want to do this hit and run?”

“He’s got that plate-glass picture window in front. Just throw it in through the window.”

“I don’t know. It’s a cul-de-sac, this street.”

“I’ll sweep it first,” Riva said. “Give me two minutes.” He pulled out into the street and headed up the hill in low.

Forrester’s house was at the bottleneck of the street just before it widened into a circular turnaround. Riva drove slowly into the turnaround. Was that a shadow in the parked car? He looked again. Nothing.

Getting nervous. He chastised himself. It would take them a lot longer than this to get men out this far. Forrester was only a junior senator from an unimportant state.

He cruised around the loop and headed out again. Glanced into the shadows of an open garage; nothing there. The snowfall had let up, the flakes were drifting down singly. He drove back over the crest and down to the mouth of the drive.

“All clear.”

4:41 A.M. EST The FBI agent spoke low into the microphone of his car radio. “Somebody’s just cased Forrester’s house. You better get another car or two up here.”

4:42 A.M. EST Harrison put the satchel charge in his lap while the car climbed the hill. He set the timer for two minutes.

Kavanagh drove past the parked Plymouth and pulled in across the front of the Senator’s driveway. “Go.”

Harrison shoved the door open and stepped out. Started to walk up the driveway toward the front of the house.

“Hold it right there. FBI.”

Harrison turned slowly on his heels, twisting his head to look over his shoulder.

The FBI man stood beside the Plymouth, aiming the pistol casually at the middle of Harrison’s coat and making it clear he felt it was an easy shot.