Premise

A mysterious event causes nearly everyone on the planet to simultaneously lose consciousness for 137 seconds, during which people see what appear to be visions of their lives approximately six months in the future—a global "flashforward". A team of Los Angeles FBI agents, led by Stanford Wedeck (Vance) and spearheaded by Mark Benford (Fiennes) and his partner Demetri Noh (Cho), begin the process of determining what happened, why, and whether it will happen again. Benford contributes a unique perspective on the investigation; in his flashforward, he saw the results of six months of investigation that he had done on the flashforward event, and he and his team use those clues to recreate the investigation.

The team investigates a number of events related to the flashforward, including "Suspect Zero", who did not lose consciousness during the event because of a Quantum entanglement device (QED), the sinister "D. Gibbons/Dyson Frost", and a similar mass loss of consciousness in Somalia in 1991. Meanwhile, personal revelations contained within the flashforwards occupy the personal lives of the principal characters. Mark Benford sees himself relapsing into alcoholism; his wife sees herself with another man; Demetri Noh sees nothing, which could mean that he will not be alive to see the day everyone else has glimpsed or, perhaps, that his future wasn't set on the day of the flashforward. Other characters grapple with similarly unexpected or surprising revelations in their flashforwards.
Characters
Main article: Characters in FlashForward (television show)

FlashForward began with nine star billed roles. From episode six on, Dominic Monaghan is billed as a regular cast member.

* Joseph Fiennes as FBI Special Agent Mark Benford – Mark's flashforward guides the investigation of the events of October 6. The husband of Olivia Benford and father of Charlie Benford, he is a recovering alcoholic. In his flashforward, he sees himself working on the Mosaic investigation when armed masked men enter his office. He also sees himself drinking, which he tries to hide from his wife.
* John Cho as FBI Special Agent Demetri Noh – Mark Benford’s partner at the FBI. He had no flashforward and fears that means he will die, especially after he receives a phone call telling him that he will be murdered. He is engaged to Zoey, a lawyer who believed her flashforward was about their wedding until she realized it was possibly his funeral. Demetri survives March 15, the date he was supposed to have been killed, thanks to Mark's assistance.
* Jack Davenport as Dr. Lloyd Simcoe – an academic at Stanford. Lloyd's estranged wife and mother of his son died during the blackout. He has a son with autism, Dylan, who knows Olivia and whom Charlie mysteriously recognizes. His research partner is Simon Campos, and Lloyd believes they are responsible for the blackout but, according to Simon's Uncle Teddy, they only amplified it, causing it to affect the whole world.
* Zachary Knighton as Dr. Bryce Varley – a surgical intern reporting to Dr. Olivia Benford. He was on the verge of committing suicide due to a diagnosis of stage 4 renal cell carcinoma (kidney cancer) when the blackout occurred. After the blackout he experiences a renewed will to live, and sees his vision as a gift. In "Course Correction", Bryce learns that his cancer is in remission.
* Peyton List as Nicole Kirby – a 19-year-old student and Charlie Benford's babysitter. She was a childhood friend of Aaron Stark's daughter, Tracy. Nicole's flashforward shows her being held underwater by a stranger. She is able to speak Japanese.
* Dominic Monaghan as Dr. Simon Campos – a quantum physicist and research partner of Stanford academic Lloyd Simcoe, who doesn't believe he is responsible for the blackout. He told people that in his flashforward he sees himself fighting and later killing a man, which was actually a lie. In "Revelation Zero (Part 2)", it is revealed that he is "Suspect Zero;" he was given a ring that kept him awake during the blackout. His uncle is the middle man in the deal, and Simon's younger sister is kidnapped by the people that want to control the blackouts. Simon's uncle had previously killed Simon's father, and after he also kills Simon's professor, Simon kills him.
* Brían F. O'Byrne as Aaron Stark – a recovering alcoholic, he is Mark Benford’s AA sponsor and close friend. His daughter, Tracy, was presumed killed in action in Afghanistan, but his flashforward showed his daughter alive. In "The Gift", he comes home to find Tracy in his living room. Agents of the military contractor Jericho later kidnap Tracy from his home, and in "The Garden of Forking Paths", Agent Wedeck provides him assistance in getting to Afghanistan to find Tracy.
* Courtney B. Vance as FBI Assistant Director Stanford Wedeck – head of the FBI Los Angeles field office. He oversees Mark Benford's team and the October 6 investigation. His flashforward shows him on a toilet reading a newspaper.
* Sonya Walger as Dr. Olivia Benford – Mark's wife and a successful surgeon at a major hospital. She supervises Dr. Bryce Varley. In her flashforward, she is romantically involved with Dr. Lloyd Simcoe, although she had never met him before the blackout. They meet when she treats his autistic son, Dylan.
* Christine Woods as FBI Special Agent Janis Hawk – works at the Los Angeles field office as part of Mark Benford's team. In her vision she was pregnant and having a sonogram, which she finds hard to believe because she is single and a lesbian. She is in charge of watching over Simon later in the series. In "Queen Sacrifice", it was revealed that she is a mole reporting to those responsible for the blackout. In "Goodbye Yellow Brick Road", it is revealed that she is actually a double agent for the FBI and CIA at Agent Vogel's request.