The Taliban foot soldiers were new to air travel.

"They were throwing up all over the place," recalls Joby Warrick, who was hitching a ride on a U.S. military helicopter taking them home to be rehabilitated in Khost, Afghanistan, in May 2010.

Warrick tried to avert his gaze in the crowded cabin. The sickly, bearded convicts, who had been pardoned after committing minor offenses, weren't his main concern.

Warrick was focused on reaching Khost and seeing the CIA base there.

He was writing a book about a 2009 suicide bombing by al-Qaida that had killed seven agency employees inside the compound and rocked the intelligence world to its core.

"The Triple Agent," is a solid hit for Warrick, a Pulitzer Prize-winning investigative reporter who graduated from Hempfield High School in 1978.

The protagonist of the true-life thriller is enigmatic Jordanian doctor Humam al-Balawi. The meek-seeming informant controlled jointly by Jordanian and American intelligence was secretly an al-Qaida mole who blew himself up inside the fortified CIA base on New Year's Eve.

"By February," Warrick says, "I was convinced there was a much bigger story to be told."

A spy story.

Warrick, a lover of the espionage writings of John le Carré and Graham Greene, was intrigued. So were his literary agent and eventual publisher, Doubleday.

Warrick negotiated six months of leave and vacation from his Washington Post desk and launched his first book project.

In 1996, Warrick and his team at the Raleigh (N.C.) News & Observer had captured a Pulitzer by exposing the underworld of factory farming.

But tracking spies through a "classified world" was especially difficult, Warrick says.

On the other hand, "Despite the secrecy surrounding this case... it was a case everybody was talking about. People were trying to figure out what went wrong, who screwed up."

• Warrick conducted hundreds of interviews. He flew to Iraq. He flew to Afghanistan, which he ranks as "one of the most intimidating environments I've ever been in."

Gradually, the diagrams he stapled to the drywall of his basement office in Washington, D.C., helped him visualize the maze.

CIA officer Darren LaBonte was suspicious of al-Balawi, Warrick learned. LaBonte's warnings went unheeded.

But Warrick says "The Triple Agent" "is not a very judgmental book."

Its mission is to shed light on the risky, complex work intelligence agents do in the name of the American people.

He learned much about James Bondian technology that can protect innocents by aborting a drone missile in midflight.

Reports Warrick: "They'll watch a house for three or four days, looking to see are there children who go in ... are there women going out for firewood."

He says official response to "The Triple Agent" has been nil, and thus good.

"They're not going to express a view unless they're terribly unhappy about something," he reasons.

Reviewer Adam Goldman, who covers intelligence and counterterrorism for The Associated Press in Washington, called the book "a riveting tale ... a must-read for counterterrorism and spy junkies."

Readers, too, are praising the book on its Facebook page, facebook.com/TheTripleAgent.

Also enduringly supportive is Warrick's former Hempfield English teacher, with whom he keeps in touch.

"My first book signing was at the Spy Museum, of all places," Warrick relates. "I came out to do my talk and there in the front row was Connie Kondravy."

But there was a downside, Warrick jokes. Kondravy took a copy of the book home with her.

"I was afraid" she would scrutinize it with a red pen and flag dangling modifiers.

• Warrick, a 51-year-old father of two who lives in Washington with his wife, Maryanne, is back on his Post beat covering national security.

The job regularly takes him to the unsettled regions of the globe with Secretary of State Hillary Clinton's entourage.

It's a "front-row seat to history," Warrick says.

These days have been "some of the craziest times of my life," he adds, referring to long hours working on "The Triple Agent."

Not to mention the danger.

Luck and pluck ultimately did get Warrick to the CIA base in Khost.

"We flew right over it" in the chopper carrying the Taliban soldiers, he says.

"You almost have to be able to taste it and smell it to be able to report authoritatively."

Contact Sunday News staff writer Jon Rutter at jrutter@lnpnews.com.