Damon Runyan stars in “Gangland Undercover”

It's a story right out of Hollywood. A man, fully immersed in the drug culture of Southern California, deals methamphetamine to the tune of more than $500,000 a year. The only direction he's headed is straight to the pen, especially after he's caught in a raid by the Drug Enforcement Agency. Except, the DEA gives him a choice: go to prison for 22 years with no chance of parole or become an undercover informant.

While it may seem almost too good to be true, there's no denying that this story did, in fact, take place. The born-again informant is none other than Charles Falco, a burly man whose exploits as an undercover operator for the DEA and Bureau of Alcohol, Tobacco, Firearms and Explosives in three of the most notoriously dangerous biker gangs in SoCal are the stuff of legends.

In 2013, Falco published a memoir detailing his rise as an undercover agent titled "Vagos, Mongols, and Outlaws: My Infiltration of America's Deadliest Biker Gangs." Now, History has created a six-episode fact-based drama that draws its material from the book and Falco himself, and offers viewers a look inside the life of this zero-turned-hero of sorts. With only one episode left, it's time to hunker down as "Gangland Undercover" brings the chills and the thrills when the season finale airs Tuesday, March 31, on History.

Falco is a fascinating man. Born and raised in Los Angeles, he saw his life take a turn for the worse that landed him at rock bottom. After being contracted by the ATF to infiltrate the Vagos in 2003 (and later the Mongols and Outlaws), he quickly rose through the ranks of the biker gangs and gathered evidence that led to 62 total arrests. Now, due to the nature of his past efforts, Falco is in the witness protection program. This, however, doesn't stop him from actively being involved in telling his story -- spearheading "Gangland," writing for the show and even appearing before each episode.

"Right from the start, he was available to me," "Gangland's" star Damon Runyan ("One Starry Christmas," 2014) told TV Media. "In preparation for the role, I could contact him at any point. When we were doing the exterior shots in Arizona, he came down and he was accessible to all of us. I still talk to him pretty much on a daily basis now."

Paulino Nunes ("The Firm," "Bitten") -- who plays Schizo, the primary antagonist in "Gangland" and the Vagos president -- says that he first met the real-life Falco when they were shooting in Arizona and was struck by how cool he was.

"He's a really super nice guy," he said in the same interview with TV Media. "I know that sounds like a kind of banal thing to say, but ... it's not necessarily what you'd expect. It was really cool meeting him, and it was hard to reconcile the guy you were meeting with the guy in the book and the guy who did all that stuff."

Paulino Nunes in “Gangland Undercover”

"All that stuff" being some truly horrific and gruesome acts he had to witness and commit, including beating up rivals, watching Vagos bikers kill rivals and civilians, selling drugs and even going to prison for an assault committed by another Vago, where he had to suffer through solitary confinement in order to avoid blowing his cover.

But through it all, Falco remained unwavering in his newfound pursuit of justice. He was given a second shot at life, and he took it. His intelligence shone through with each day that he went deeper undercover, and it's something that was not lost on Nunes or Runyan as they acted out his story.

"He's a keen observer of human nature, and he had to be to do what he did," Nunes said. "It was pretty apparent that this was a guy who, if his circumstances had been different, could have done something very different with his life. As it turned out, because of the bad choices that he made early on, this was kind of his shot at redemption, going into the situation and taking these guys down."

"His intelligence is the thing that kept him alive and also was able to allow him to get so deep," Runyan added, "and not only do one gang, but three gangs."

These days, Falco has put his active undercover work behind him. He's since earned a graduate degree in criminal justice and works as an instructor for a national law enforcement training institute, not to mention adding "Gangland" to his resumé. Of course, for him, there'll always be a nagging fear for his safety.

"I think you always have to fear for your safety," Falco said in an interview with "Los Angeles Magazine." "I have a witness protection program ID that I use. I don't hang out in bars. I don't live in an area where any of these groups live. You've got to always look over your back."

Catch the season finale of "Gangland Undercover" when it airs Tuesday, March 31, on History.