"MARATHON: THE PATRIOTS DAY BOMBING," AN UNFLINCHING PORTRAIT OF SURVIVORS OF THE 2013 BOSTON MARATHON ATTACKS, DEBUTS NOV. 21 ON HBO

April 15, 2013 was a picture-perfect day for the 117th annual Boston Marathon, held on Patriots Day, which commemorates the first battle of the Revolutionary War. Spectators were gathered on Boylston St. in hopes of seeing top racers and loved ones cross the finish line. But at 2:39 p.m., two bombs detonated 12 seconds apart.

MARATHON: THE PATRIOTS DAY BOMBING recounts the dramatic story of the Boston Marathon terrorist attacks through the emotional experiences of individuals whose lives were forever changed by them when it debuts MONDAY, NOV. 21 (8:00-10:00 p.m. ET/PT). Ranging from the events of the day to the death-penalty sentencing of Dzhokhar Tsarnaev, the documentary features surveillance footage, news clips, home movies and exclusive interviews with survivors and their families, as well as first responders, investigators, government officials and reporters from the Boston Globe, which won a Pulitzer Prize for its coverage.

In the wake of a heinous act of terrorism, a newlywed couple, a mother and daughter, and two brothers - all gravely injured by the blast - face the enormous challenges of physical and emotional recovery, over the course of three years, as they and their families strive to reclaim their lives and community.

Other HBO playdates: Nov. 23 (2:00 p.m., 2:45 a.m.), 26 (4:00 p.m.) and 29 (11:30 a.m.), and Dec. 1 (4:00 p.m.), 3 (1:35 p.m.) and 6 (1:00 a.m.)

HBO2 playdates: Nov. 29 (8:00 p.m.) and Dec. 8 (2:00 a.m.) and 19 (4:05 p.m.)

The documentary will also be available on HBO NOW, HBO GO, HBO On Demand and affiliate portals.

Directed by Emmy(R) nominees Ricki Stern and Annie Sundberg (HBO's "Burma Soldier"), and produced in association with the Boston Globe, this feature documentary focuses on how the attack changed the lives of three families, including five survivors who lost one or both legs. MARATHON: THE PATRIOTS DAY BOMBING goes behind the scenes of their painful, often-frustrating rehabilitation, juxtaposing these stories with efforts of the police and FBI to identify and hunt down the perpetrators.

Among the families spotlighted are:

The Corcoran family. Celeste Corcoran joined her husband, Kevin, daughter, Sydney, and son, Tyler, at the marathon finish line because her sister was running. Celeste lost both legs. Sydney sustained critical injuries and, although her wounds were ultimately not as visible, suffered extreme PTSD. Kevin also struggled to deal with witnessing the pain experienced by his wife and daughter.

The Norden family. Brothers Paul and JP Norden both lost a right leg in the second explosion, a video of which their mother Liz estimates she has watched "3,000 times." The brothers were in surgery at the same time, and Paul was in a medically induced coma for nine days. JP's recovery was torturous - he had burns over 50% of his body - and he felt guilty that his fiancée, Kelly, had to deal with his misfortune. In 2015, JP and Kelly were married; many bombing survivors attended the wedding.

The Downes and Kensky families. Newlyweds Jessica Kensky and Patrick Downes both ran the Boston Marathon in 2005. In 2013, they decided to enjoy the race as spectators. Both lost a leg in the bombings. After receiving physical therapy with Patrick at Walter Reed National Military Medical Center in Bethesda, Md., Jessica decided to amputate her other leg, which had been badly damaged in the blast, when the pain became too much to bear. She has endured periods of depression, but Rescue, their service dog, helps them cope. Jessica was resolved to be at the finish line when her husband, wearing a racing blade, completed the 2016 Boston Marathon.

Other interviewees include Boston Globe photographer John Tlumacki, who befriended the Corcorans after apologizing to them for taking graphic photos of the wounded Sydney and Celeste, which were published around the world; FBI Special Agent Kieran Ramsey; former Massachusetts governor Deval Patrick; and Boston Globe reporters Eric Moskowitz, David Filipov, David Abel and Patricia Wen, and columnist Kevin Cullen.

MARATHON: THE PATRIOTS DAY BOMBING is dedicated to the memory of those who died in the attacks: eight-year-old Martin Richard, a third-grader; 29-year-old Krystle Campbell, a restaurant manager; 23-year-old Lu Lingzi, a Boston University grad student; and 27-year-old MIT police officer Sean Collier, who was shot to death in his patrol car by the bombers three days later.

Ricki Stern and Annie Sundberg's previous credits include the HBO Documentary Films "Burma Soldier" and "The Trials of Darryl Hunt." Their other films include "Joan Rivers: A Piece of Work," "The Devil Came on Horseback" and "Knuckleball!"

MARATHON: THE PATRIOTS DAY BOMBING was produced in association with the Boston Globe; directed by Ricki Stern & Annie Sundberg; produced by Ricki Stern, Annie Sundberg, Jake Abraham and Jameka Autry; For HBO: executive producer, Sheila Nevins; senior producer, Nancy Abraham; edited by Keiko Deguchi; music by Paul Brill.