The Looming Tower, Hulu's limited series adaptation of Lawrence Wright's Pulitzer Prize-winning book about the rise of Al-Qaeda in the years before 9/11 and the FBI and the CIA's failure to work together to prevent that attack, premiered its first three episodes Feb. 28.

The limited series' showrunner Dan Futterman told TV Guide that he doesn't consider the show to be a work of fiction, but rather a dramatization of true events for which every deviation from fact has a very detailed, lawyer-approved explanation of how and why. The book and the show have hundreds of characters, and the big challenge of Futterman's in adapting the book was to figure out which characters and storylines to follow and how to condense them. Many of the characters on the show are real people, while others are composites.

This is a guide to provide some context as to who the myriad people you'll meet throughout The Looming Tower are, and which of the major characters are real and which are creations, as well as who they are in the historical record that the show can't fully contextualize and where they are now.

John O'Neill (Jeff Daniels)

Jeff Daniels, <em>The Looming Tower</em>Jeff Daniels, The Looming Tower


O'Neill was an FBI agent who was in charge of the bureau's counterterrorism division in New York. He investigated the embassy bombings in Africa in 1998 and the bombing of the USS Cole in Yemen in 2000. He repeatedly warned of the threat posed by Osama bin Laden, but he was not listened to as closely as he should have been. He was forced out of the FBI in the summer of 2001 and started a job as the head of security for the World Trade Center on August 23. He died on 9/11 while helping people evacuate from the North Tower.

There's truth to the show's depiction of O'Neill as a larger-than-life hard-drinking womanizer; he really did have multiple affairs and got in trouble with the FBI for allowing his girlfriend to enter an FBI safehouse.

Ali Soufan (Tahar Rahim)

Tahar Rahim, <em>The Looming Tower</em>Tahar Rahim, The Looming Tower

Soufan was born in Lebanon and joined the FBI in 1997. He also worked on the embassy and USS Cole investigations, and the fact that he was one of the only people in the bureau who spoke Arabic aided his brilliant investigative abilities. Lawrence Wright has written that Soufan came closer than anyone to preventing 9/11, but he was thwarted by the FBI and the CIA's rivalry when the CIA didn't share intelligence on the jihadi called Khallad — who Soufan knew was the mastermind of the Cole bombing — until months after 9/11, when if he had gotten it earlier he could have connected the Cole bombing to a planned attack on American soil.

Soufan left the FBI in 2005 and has become an outspoken critic of the intelligence agencies' failure to work together as well as the CIA's use of torture. He's the CEO of the Soufan Group, a private intelligence company he founded, as well as an author of two books about terrorism. He's a consulting producer on The Looming Tower.

Martin Schmidt (Peter Sarsgaard)

Peter Sarsgaard, <em>The Looming Tower</em>Peter Sarsgaard, The Looming Tower

Schmidt is a composite character who Futterman says represents the point of view within the CIA of people who advocated for an aggressive approach to dealing with Osama bin Laden. Though he's named after Futterman's uncle, he's most directly based on Michael Scheuer, who, like Schmidt, led the CIA's Bin Laden Issue Station, aka Alec Station — the unit dedicated to tracking bin Laden — and clashed with John O'Neill on how to deal with the threat of Al-Qaeda. Schmidt has remained a very controversial figure in the foreign policy community for his staunch non-interventionism. He resigned from the CIA in 2004 after being outed as the anonymous author of the book Imperial Hubris, which criticized the United States' approach to the War on Terror. Wright says producers reached out to Scheuer to offer his perspective for The Looming Tower, but he declined.

Diane Marsh (Wrenn Schmidt)

Wrenn Schmidt, <em>The Looming Tower</em>Wrenn Schmidt, The Looming Tower

Futterman says that Diane Marsh is "at least three people" within the CIA. The best-known real person is Alfreda Frances Bikowsky, who worked under Scheuer at Alec Station before becoming the chief in 2003 (and marrying Scheuer in 2014). Bikowsky thwarted cooperation between the FBI and the CIA before 9/11, and after becoming chief of Alec Station was deeply involved in the rendition and torture of terror suspects. She's also one of the people on whom Jessica Chastain's character in Zero Dark Thirty was based.

Richard Clarke (Michael Stuhlbarg)

Michael Stuhlbarg, <em>The Looming Tower</em>Michael Stuhlbarg, The Looming Tower

Clarke was Chairman of the Counterterrorism Security Group under President Clinton and both Bushes, as well as Clinton's chief counterterrorism adviser on the National Security Council. Michael Scheuer was very critical of him for his cautiousness in dealing with bin Laden before 9/11. Clarke, in turn, was very critical of the Bush administration's failure to act on intelligence in the summer of 2001 that warned of an impending attack as well as its handling of the War on Terror after 9/11. He apologized to the loved ones and victims of 9/11 for failing to protect them while testifying before the 9/11 Commission in 2004, saying "We tried hard, but that doesn't matter because we failed." He's now a leading expert on cybersecurity, and warns that Russia will interfere with the 2018 and 2020 elections, just like it did in the 2016 election.

Bob Chesney (Bill Camp)

Bill Camp, <em>The Looming Tower</em>Bill Camp, The Looming Tower

FBI agent Bob Chesney is the most composited of The Looming Tower's main characters. "Ali Soufan was watching the first three episodes and he called me afterwards and said, 'Okay, Bob Chesney is at least four people,'" says Futterman. "We'll see how many more he is as the show goes on." More than anything, Chesney is the representation of "good police" — that is, a dutiful and resourceful operative.

Vince Stuart (Louis Cancelmi)

Louis Cancelmi, <em>The Looming Tower</em>Louis Cancelmi, The Looming Tower

One of the real people this FBI character is based on is Mark Rossini, who was an FBI liaison to Alec Station. A CIA agent named Michael Anne Casey prevented Rossini from passing along information on two Al-Qaeda members with US visas. Those men later became 9/11 hijackers. Rossini left the FBI in 2008 after pleading guilty to criminally accessing records in an FBI database for personal purposes.

Mohamed Al-Owhali (Youssef Beroauin)

Youssef Berouain, <em>The Looming Tower</em>Youssef Berouain, The Looming Tower

Al-Owhali is a British-born Saudi terrorist who survived the embassy bombing in Nairobi because he ran away from the truck after throwing a stun grenade at the guards. He cooperated with the FBI's Al Qaeda investigation and is currently serving a life sentence at the ADX Florence federal supermax prison for his role in the bombing.

George Tenet (Alec Baldwin)

Alec Baldwin, <em>The Looming Tower</em>Alec Baldwin, The Looming Tower

Tenet was the CIA director under Presidents Clinton and George W. Bush. After the embassy bombings he "declared war" on Osama bin Laden but was unsuccessful at capturing him. He left the CIA in 2004. President Bush awarded him the Presidential Medal of Freedom and the New York Times Editorial Board has said he should be criminally investigated for his role in the CIA's torture program after 9/11. He also was randomly shouted out in a Kanye West song once.

The first three episodes of The Looming Tower are now streaming on Hulu. The seven subsequent episodes will premiere on Wednesdays.