WASHINGTON – Spring had come to Washington, but there was a slight chill in the air. It was an overcast, sleepy day, and the highlight of the president's schedule was an otherwise unmemorable speech to a construction trades union at a hotel just a mile from the White House.

As he was leaving the hotel that afternoon, however, a madman suddenly fired off six shots – emptying his handgun in less than two seconds – before Secret Service agents and other lawmen could wrestle him to the ground. One .22-caliber bullet hit the president in the chest, ripping through muscles and a lung before lodging one inch from his heart.

The head of his security detail pushed him head first into an armor-plated black Lincoln limousine and ordered the driver to rush to the hospital. The president, 70, was coughing up blood. At the emergency room, he gasped for air and lost consciousness.

It did not look good.

Meanwhile, the vice president was some 1,500 miles away in Fort Worth, Texas. Confusion reigned in the White House over who was in charge and who was behind the assassination attempt. The new president had been sworn in to office just 70 days earlier, and there was talk of conspiracy. His national security team feared the shooting could be part of a KGB plot to overthrow the U.S. government.

They had good reason to worry.

U.S. intelligence showed the Soviets suspiciously amassing nuclear submarines off the East Coast, and one of those subs was closer than normal. What's more, Soviet troops seemed poised to invade Poland to put down a growing labor-reform movement there.

In response to the possible threat, the secretary of defense raised the level of readiness of U.S. forces from DEFCON 5 to DEFCON 4.

What sounds like a Tom Clancy novel happened more than 23 years ago – March 30, 1981 – the day President Ronald Wilson Reagan was shot. Unknown to the public at the time, America was not far from the brink of nuclear war with the Soviet Union, the "Evil Empire," as Reagan called it.

Yet the secret codes the late president would need to authorize a nuclear strike went missing – for nearly two days. And no one in the White House knew their exact whereabouts.

As it turns out, they ended up across town in a safe following a nasty bureaucratic tussle for them, a former FBI official who personally handled the critical data says in an exclusive interview, breaking two decades of silence about the mystery.

First, rewind to 2:35 p.m. on that tragic day. A wounded Reagan had bravely stepped, unassisted, from his limousine before collapsing in the emergency room at George Washington University Hospital. Absent from the group traveling with him in the motorcade that pulled up to the entrance was his military aide who carried the nuclear "football" – the black briefcase containing the Top Secret options and orders the president needed to launch a nuclear attack. (The orders are different from the personal verification codes Reagan kept in his breast pocket, which authenticated the nuclear strike orders.) The football is supposed to be kept at the commander in chief's side at all times.

But the aide, Lt. Col. Jose Muratti Jr., also known as the emergency war orders officer, was separated from Reagan and his motorcade during the shooting at the Washington Hilton, and had to take another car to the hospital. Not long after he arrived there, National Security Adviser Richard Allen had the football brought to him at the White House. He and other principals were gathered in the Situation Room.

"I held it in my hand," Allen recounted in an interview on the 20th anniversary of the assassination attempt. "It was under my sheaf of papers, and stayed right there all afternoon. It didn't pass into the hands of anyone else."

Unfortunately, the same could not be said for Reagan's equally important code card. The card, which contains a series of coded numbers and words, is the only device personally carried by the commander in chief to identify himself to Pentagon brass in the war room officially known as the National Military Command Center.

In all the panic, his staff had neglected to secure it.

Back at the hospital, emergency room nurses who attended the gravely wounded president stripped away his clothing. They sheared off his brand-new blue pinstripe suit and white shirt with a pair of surgical scissors. The shredded suit coat fell to the floor, where it was trampled underfoot by the trauma team. Inside its breast pocket was the code card, which went largely unnoticed in the scramble to rush Reagan into the operating room.

Secret Service agents gathered up his personal belongings in a plastic bag as he was prepped for surgery. Not long after that, at least four FBI agents arrived to gather evidence for the bureau's investigation of the assassination attempt. They were led by James "Jim" Werth, a young agent detailed that day to catalog evidence gathered at the hospital. His supervisor that day was I.C. Smith, a relatively junior counterintelligence manager at the Washington field office. He was left in charge of the investigation throughout that anxious night.

As Werth was sifting through Reagan's effects at a makeshift evidence room set up in the hospital, he discovered the nuclear launch codes in the pocket of the tattered suit coat. At that point, Reagan's military aide, Muratti, along with Edward V. Hickey Jr., a White House security aide, realized they had overlooked the card and demanded Werth turn it over to them.

But in a heated exchange, Werth refused after checking with Smith by phone from the hospital. The bureau has investigative jurisdiction over attacks on the president. Smith, now retired, gave the order to seize the card after consulting with headquarters.

When he got the call from Werth, he was furiously scribbling notes onto 3-by-5 index cards from reams of teletypes coming into the command center at the field office from around the country. One of the more important pieces of information Smith had flagged for the FBI's special agent in charge, whom he briefed the following morning, was how the shooter – a loner by the name of John Hinckley Jr. – had bought so-called "devastator" bullets.

"These were designed to explode once they go in, so I said, 'For God's sake, get in touch with the surgeon and let them know what they've got their hands on,'" he recalls telling agents back at the hospital. Luckily, the .22 bullet, which had ricocheted off the armor of the limousine, had not exploded after it sliced into Reagan's chest, entering just under his left armpit.

Still, what Werth reported back was not encouraging. "Boy, he may not make it," he told Smith.

Not long after that, Werth called Smith again with urgent news. Agents had found Reagan's "doomsday codes" in the mess of clothing. They were kept inside a heavy stock envelope slightly larger than a standard security business envelope.

"We've got this envelope," Werth said, "and all these old staff guys want it, and we don't know if they're authorized to get the codes or not."

"You bring them to me," Smith ordered. "We are not going to turn them over to some (White House) staffer."

Werth then brought the envelope containing the secret codes to the field office, which at the time was located in a building at Buzzard Point in southwest Washington. He walked into the office carrying them in a manner Smith says he will never forget.

"He shows up holding these things as if he's holding an egg or something – very gingerly," Smith chuckled.

"And I opened the top drawer of the safe and we placed them in it, and I closed the safe and spun the dial," he said in his Southern drawl.

There they remained, across town from the president, overnight.

Smith says the White House staffers, who he described as "snippy," were furious that the FBI was seizing control of such a sensitive national security document.

Indeed, they argued the code card wasn't tied to the shooting and had no possible value as evidence in the investigation. And the Reagan aides accused the move to secure the codes as an unnecessary bureaucratic reaction.

"Some of his snippy White House staffers were demanding they be turned over to them," recalled Smith. "I called FBI headquarters and told them the situation and recommended that they bring the codes to the Washington field office where we could keep them until we could sort out who has authority to have them. And that's what we did."

He explains that part of his job as a counterespionage official was to also make sure the nuclear launch codes were not compromised and did not fall into the wrong hands.

"I was also responsible for maintaining the secrecy of the doomsday codes in Reagan's pocket, particularly by keeping them away from his staff," said Smith, whose order was backed up at the time by Attorney General William French Smith. He adds that he did not want the FBI to be accused of turning over the codes to some staff member at the White House with no authority to have them.

The next day, he gave the code card to the special agent in charge of the Washington field office at the time, Ted Gardner, who had left Smith in charge the previous evening.

It's not clear if a new card with a new set of codes was issued or if the national security of the U.S. was impaired at any time during that frantic and perilous period.

Surgeons removed the bullet from Reagan's chest in four hours, which is how long he was under general anesthesia. What if, while he was recovering, the Soviets had fired nuclear missiles at America from their subs positioned off the East Coast or elsewhere? Pentagon officials would have been unable to match corresponding codes in their war room to ensure that any counterstrike Reagan ordered from an unsecure hospital phone was authentic.

Even so, Smith argues that the nuclear warfare responsibility would likely have passed to then-Vice President George H.W. Bush, who had his own set of codes, since Reagan would have been under heavy sedation for pain during his recovery.

Smith reveals more details about his historic dust-up with the White House and the investigation of crazed gunman Hinckley in a new memoir about his long FBI career. Titled, "Inside: A Top G-Man Exposes Spies, Lies and Bureaucratic Bungling Inside the FBI," the book was recently released by Nelson Current.

The mystery of the lost code card has been solved. But to this day, Smith notes that one of the gold cuff links Reagan was wearing when he was shot – part of a favorite set of his shaped like the golden bear of California – has never been found.

"At one point Jim Werth called and said they couldn't find his darn cuff link," Smith said. "Never did find it. Never did."

It didn't make it into the FBI safe with the nuclear key card, which thankfully was never needed.

Still, he says, the public was unaware of the potential crisis, and was never told how close Reagan came to dying that dark day.

"I went home drained the next morning," Smith recalled. "I'd been drinking coffee all night and I was just wired. I couldn't sleep and just lay there in bed, my eyes big as saucers, because I wasn't sure the president was going to make it. Before I left that morning, we still weren't sure he was going to make it.

"The public never realized how close Reagan came to dying," he said.