Sebastian Rotella is an award-winning investigative reporter who, for more than a quarter-century, has covered politics, crime and corruption throughout Latin America. In 1998 he published a highly praised book of nonfiction called “Twilight on the Line: Underworlds and Politics at the U.S-Mexico Border.” Now, he has turned to fiction to dramatize the violence and venality of the border and the drug trade, even as he honors the honest cops in both countries who resist the power of the cartels.

“Triple Crossing” starts in San Diego, where we meet Valentine Pescatore, a young Border Patrol agent who’s both big-hearted and hot-tempered. We see the former quality when he slips money to illegal aliens he’s just arrested. We see the temper when he chases a smuggler he dislikes back across the border into Tijuana, a violation that could get him fired or even jailed. Through Valentine’s skeptical eyes, we watch what he calls the border’s “nightly battle theater of the absurd.” He particularly loathes his boss, who beats up on illegals even as he takes bribes from smugglers.

After Valentine’s wild-man raid into Tijuana, he is summoned by a higher-up Border Patrol official, a sexy Cuban-American named Isabel Puente, who instead of firing him, recruits him to spy on his crooked boss. On the other side of the border, we meet Leo Mendez, a former journalist who now leads an elite government anti-corruption unit. This trio joins forces to bring down an uncle and nephew who lead one of Mexico’s most powerful drug cartels. The uncle, called The Senator, is a powerful politician. The nephew, called Junior, is a decadent young drug lord who controls a small army of Tijuana narco-thugs who indifferently kill journalists, police, politicians or anyone else their boss wants eliminated. The Death Patrol, they call themselves.

Valentine infiltrates Junior’s army by winning the trust of his top enforcer. We’re given a chilling picture of young assassins who may kill one day and spend the rest of the week getting high and watching TV. Events carry the novel’s main characters from Mexico to the Triple Border, a lawless zone where Argentina, Paraguay and Brazil meet. Crime has become globalized, Rotella is warning, and crime lords from all over the world gather to target America with their smuggling of drugs, guns and humans, as well as money-laundering, Internet scams, assassinations and innumerable other crimes.

In this hotbed of criminality, the two honest cops, Isabel and Mendez, aided by a few honest local officials, set out to arrest Junior. Or will Junior’s soldiers find and kill them? Further complicating matters, it’s unclear whether Valentine, still part of the drug lord’s entourage, remains an undercover agent or has gone over to the dark side.

Rotella knows how the police work, how the criminals operate and how bribes and violence subvert the law. He employs a journalist’s sharp eye and a novelist’s deft touch to give us a rich portrait of the sights, smells, sounds, beauties and dangers of life south of the border. In one of the novel’s most terrifying scenes, the truth-seeking Isabel and Mendez risk their lives to venture into the hell of a Mexican prison, where the inmates have all the women, drugs and weapons they can pay for. In this novel, idealists are sometimes gunned down in cold blood. The crusading officials are the book’s heroes, but the ruthlessness of the cartels makes anarchy seem an ever-present threat.

I had a few, relatively minor reservations about the novel. One love affair that becomes important to the plot struck me as improbable, although I will grant that logic does not always guide these matters. Beyond that, Rotella overworks some words and phrases, as his editor should have noted. We’re told far too often that the loathsome Junior is fat, flabby, jowly, sloppy and big-bellied, and that he uses disgusting cologne and spits all the time. And then there are the ears. Throughout the novel, the cartel’s thugs repeatedly threaten to cut off someone’s ears and make him eat them. Then, near the end — heaven help us — one of them sets out to do just that.

For the most part, however, this is an honest and engrossing journey into a world of violence and corruption that is a threat to our own well-being. Recent news reports that our government plans to expand its already huge financial support for Mexican anti-cartel efforts is an indication of the dangers we face. Reading “Triple Crossing,” I was reminded of movies — “Scarface,“Blow,” “Traffic” — that take a panoramic look at the drug trade. As it happens, John Malkovich’s production company has bought the rights to the novel and plans to convert it into a miniseries. It could be a good one.