The life of David Coleman Headley, a self-confessed American terrorist and Pakistani spy, has moved from soap opera to crime story to espionage thriller.

Monday begins the most revealing chapter yet: the courtroom drama.

Headley, a Pakistani American businessman and former informant for the Drug Enforcement Administration, will be the star witness against Tahawwur Rana of Chicago, his boyhood friend and alleged accomplice in the 2008 Mumbai terrorist attacks. Opening arguments are set for Monday in a trial that has drawn international attention because Headley’s testimony could reinforce allegations that Pakistan plays a double game in the terrorism fight.

The prosecution will depend largely on how the jury views Headley. The burly 50-year-old has a swashbuckling personality and a knack for juggling relationships with multiple wives, terrorist groups, and law enforcement and intelligence agencies.

“Sometimes he’d tell my husband, ‘Oh, I want to be in movies,’ a movie star or something like that,” Rana’s wife, Samraz, told ProPublica and PBS’s “Frontline.” “So it looks like he wants to be famous.”

Headley pleaded guilty last year to conducting reconnaissance for the Mumbai attacks, which killed 166 people, and plotting against Denmark. His confessions painted a devastating portrait of Pakistan’s Inter-Services Intelligence Directorate (ISI), because he said ISI officers helped the Lashkar-i-Taiba terrorist group plot the commando-style Mumbai attacks.

Rana’s defense centers on ISI links. His attorneys say Headley convinced Rana that he was part of an ISI operation in India, then betrayed him to escape the death penalty.

“They are using a whale to catch a minnow,” said Charles Swift, Rana’s attorney. He called Headley “a master manipulator.”

Prosecutors recently raised the political stakes by indicting a suspected ISI officer in the deaths of six Americans in the Mumbai attacks. The officer, identified only as Maj. Iqbal, was charged last month, along with three alleged Lashkar masterminds of the attacks. The indictment, decided at high levels in Washington, sent a tough signal to Pakistan shortly before the raid that killed terrorist leader Osama bin Laden in a military town near Islamabad, the Pakistani capital.

“I think it shows the government believes Headley when he says his handler was an ISI officer,” said James Kreindler, a former federal prosecutor who is suing the ISI in New York on behalf of victims of the Mumbai attacks and their families.

Pakistani officials deny any links to terrorism and question Headley’s credibility.

Rana, a doctor by training, is the lowest-ranking suspect among those indicted. He is charged with material support of terrorism for allegedly letting Headley use his immigration consulting firm as a cover overseas.

Rana has known Headley since they attended an elite military school in Pakistan. When the DEA arrested Headley in 1988 and 1997 on heroin-trafficking charges, Rana put up his house as bond.

Rana’s wife, who also has a medical degree, met Headley in the 1990s. The convicted heroin dealer and recovering addict charmed her conservative immigrant family, she said during the interview.

“He was a tall, handsome guy,” she said. “He was wearing very expensive clothes, and, I mean, he was really impressive.”

Headley’s mother came from a rich Philadelphia family, and his father was an influential Pakistani broadcaster. Headley told investigators that he has a distant Pakistani relative who was a former ISI deputy director, according to Indian and U.S. officials. If that link is confirmed, it could help explain why — according to his confession — the ISI recruited Headley and how he had access to senior officers and militant chiefs.

In the late 1990s, Headley became a prized DEA informant, targeting Pakistani drug traffickers. Immediately after the Sept. 11, 2001, attacks, the DEA told him to collect intelligence on terrorists as well. The government ended his probation three years early, in December 2001, and rushed him to Pakistan. There, according to documents and officials, he began training with Lashkar.

Some federal officials say he remained an informant for at least three more years, but the DEA says he was deactivated in early 2002. The trial is likely to explore the mysteries of his work as an informant.

Headley has four children with a Pakistani wife from an arranged marriage in 1999. But he has been married to three other women, and several of those relationships overlapped.

At times, he has worn a full beard and traditional garb and expressed warlike beliefs, quoting the Koran and praising the terrorist group al-Qaeda. But he has often gone clean-shaven and behaved like a high-rolling entrepreneur.

When the Ranas ran into financial trouble in 2005, Headley rescued them with a loan of more than $60,000, Samraz Rana said.

In 2006, the ISI recruited Headley in Pakistan, according to his confession to Indian authorities. He said he met two colonels and two majors, including his trainer and handler, Maj. Iqbal, who gave him about $28,000 to establish a front office — allegedly using Rana’s firm as a cover — in Mumbai. Iqbal and Lashkar directed his reconnaissance, the indictment says.

Rana’s wife insists that her husband had no idea about the plot. The Ranas visited family in Mumbai days before the November 2008 attacks.

“My relatives are there,” she said. “I was there. My husband was there. We [could have been] killed in that attack.”

The defense, however, will have to explain evidence indicating that Rana praised the masterminds of the Mumbai attacks, communicated with Maj. Iqbal and helped Headley’s undercover scouting in Denmark.

Shortly before the Mumbai attacks, Headley had brought his Pakistani wife and children to Chicago. They lived with the Ranas for 20 days.

The FBI arrested Headley and Rana in October 2009. Headley quickly cooperated and spent weeks detailing his role in the Mumbai attacks.

“If you see him, you cannot even imagine that he can do things like that,” Samraz Rana said. “I mean he talks so good. He’s so polite.”

Now, though, Rana’s wife sees Headley as a predator.

“He just thinks about himself,” she said.

This report is part of an investigation by ProPublica and PBS’s “Frontline.” ProPublica is a nonprofit newsroom that produces investigative journalism.