Five astronauts are sole survivors of an inexplicable apocalyptic event that caused Earth to suddenly blow up. An alien AI construct that's investigating similar incidents arrives and sends them five years into the past to stop the event.
The crew tries to prevent the suicide of a notable mathematician who developed sentient AI programs. Sarah and Angela investigate a suspicious gene therapy treatment. Neil returns to high school and meets his now underage girlfriend.
Fearing it might destroy Earth, Chuck plans to sabotage NASA's new satellite project Bright Sky. Sarah tries to prevent a crime that happened in the original timeline but now it happens differently. Kurt finds a way to detect synthetics.
Someone tips the crew on how to find the missing deaf niece of a scientist who worked on mind control technology. Sarah meets the man whom she married in the original timeline. Marc passes NASA's first test. Angela deals with her folks.
The crew has visions of people asking them if they believe that anything is possible. This leads to Chuck and Neil confronting a painful memory, Sarah dealing with her son's cancer and Kurt and Angela seeing the future they could've had.
Neil's classmate hooks Niel's girlfriend and some other kids on a strange psychoactive drug that seemingly makes people smarter. Chuck learns that NASA's new flight director is part of "The Cadre" cabal. Angela's psych evaluation is up.
Chuck, Kurt and Sarah infiltrate a private high tech prison called Lock Down Unit 7 to find the convict who claims that the people he killed were synthetic replicas of his parents. Neil's brother is having identity crisis.
Chuck gets infected by a synthetic and starts turning into one. The other synthetics want him to join them. Sarah tries to get joint custody of her son, after his father takes him away. Marc is tested by his supervisor.
Neil is being stalked by Kit-10, an insane all-powerful female AI. Sarah loses her visitation rights. Angela is on a new joint space mission with a friendly Russian astronaut, Tatianna Kosviskova. Kit-10 uses them as hostages.
Man-made artificially intelligent synthetic organism that imitates human skin and can attach itself to a person and take them over jumps from one person to another in an attempt to kill Angela's father. Chuck's worst nightmare comes true.
Chuck takes a trip down memory lane with a young female hitchhiker. Kurt grows a human-synthetic hybrid. It attacks him and escapes. He suffers a mental breakdown and becomes convinced that the crew has been replaced by synthetics.
Chuck suddenly wakes up in a hospital with his dead wife by his side. She claims that it was he who almost died, not she. Sarah and Angela investigate a mass grave tied to a Transhumanist group. Neil looses his virginity - again.
A group of children who all visit the same computer lab receive a strange signal over the Internet and become obsessed with it to the point of killing anyone who tries to interfere. Chuck's estranged sister helps him deal with his grief.
Dr. Chandra dies under suspicious circumstances and leaves the crew a disk that synthetics want. The crew investigates what caused a strange riot in a peaceful suburbanite neighborhood in the original timeline and tries to prevent it.
Chuck analyzes a strange Moon rock concealed by NASA and finally gets some answers. Angela is kidnapped. A cop falsely suspects Kurt. Sarah's wish comes true - as well as her worst nightmare. The show ends on an unresolved cliffhanger.