Secret Service Secrets. The name of the agency lends itself to mystery, and lately, scrutiny. Dozens of agents are under investigation for a series of scandals that may have happened while on an "advance trip" to Columbia, ahead of the President's visit there.

Whether the issue is systemic is still up for debate. What is not? The loyalty of the men and women who sometimes give their entire lives to work in the Secret Service.

Men like Bill Mattman.

"(People) just see the president arrives and gets into a car. Well, that doesn't just happen," Mattman says.

The route is checked out.

"There's surveillance going on. You go into a restaurant, there are agents there ahead of you."

When the entourage crosses railroad tracks, "You find out what time the freight train comes by."

Manhole covers are checked and sealed.

"You cover all your bases. And you always have a backup plan. Two or three."

That's the pressure of the United States Secret Service. Mattman gave 13 years of his life to the agency. Recruited from the U.S. Border Patrol in 1967, Mattman was one of the first naturalized agents in the agency. He was born in Switzerland and spoke several languages. It was a skill in high demand.

But the job was not always as glamorous as many films depict it to be.

"I had to cancel many parties, many dinners," says Mattman. "I was not home for the kids birthdays or little league games. I missed quite a few anniversaries."

Secret Service agents have one of the most high-profile law enforcement jobs in the world, and also the most mysterious.

"[Agents are] extremely loyal. They're extremely dedicated to their work, and they will never shy away from what needs to be done."

The Secret Service began after the Civil War to combat counterfeiting, although it's best known for protecting the president. Mattman did just that during the tenure of Presidents Johnson, Nixon, Ford and Carter. Assigned to the Paris office, Mattman was also responsible for protecting visiting dignitaries. Among them, Henry Kissinger, King Hussein of Jordan, even Yassir Arafat.

"No matter who that person is, you're willing to step in front of them and take the proverbial bullet," Mattman says.

And in some cases, the bullets and the threats are very real.

Rewind to May, 1979, Los Angeles.

Agent Mattman worked the crowd as President Jimmy Carter prepared to give a speech. He had a roving post, and noticed a man wearing a heavy, ill-fitting suit on a very warm day. Mattman "felt a gun in his back pocket. President Carter came out at that very moment. So I just had to get him out of the way."

The gunman eventually told Mattman that the day before, he'd been approached by two men, who told him "to just fire a cap pistol at stage right when the president was speaking so they could fire shotguns from stage left after all the security moved over to respond to the cap pistol."

Agents went to the man's room in downtown L.A. and found the shotgun case and shotgun shells. Raymond Lee Harvey, known as the "Scarlett Sparrow," wrote Mattman a note from prison.

"His accomplice, according to hotel records, was Oswaldo Espinoza," recounts Mattman. "Kind of made your hair stand up on the back of your neck."

Authorities never found Oswaldo Espinoza.

Mattman left the Agency before President Reagan's more high-profile assassination attempt. Reagan was governor, campaigning in New Hampshire when Mattman had an encounter with him.

"One evening, there was a knock on the door. [Reagan] asked me if I'd seen this magazine," Mattman shows off an old edition of People. "I said no, and he said, your pretty face is in there." Mattman laughs, recalling the visit. Reagan offered to sign the magazine.