The crew members of the Odyssey 5 space shuttle witness the explosion of Earth from an orbit far above. They are rescued by The Seeker and given the chance to save Earth. The Seeker sends them 5 years into the past to attempt to avert the destruction of the planet.

The crew attempts to go back to their lives of five years prior to the destruction of the Earth, while also trying to begin their investigation.

The Odyssey 5 team tries to locate Professor Naran Chandra, an artificial life researcher who in the original timeline will commit suicide at a lecture 8 days from now, right in front of Kurt. Examining the files on Chandra's computer, they find that Chandra discovered a computer lifeform loose on the Internet that apparently evolved on its own from experiments in Chandra's lab and has now become "Sentient".

Meanwhile, noting how mature and responsible his behavior has suddenly become, Neil's girlfriend Holly talks about taking their relationship to the next level.

Sarah and Angela's investigation of the patients given "gene therapy" by Dr. Barantz leads them to discover some living tissue that appears to have been bio-manufactured in a chemical vat. Then, when they finally meet the frightened Dr. Chandra, the team discovers that one of his students is actually an inhuman creature made from this same nearly-indestructible tissue.

NASA's Project Bright-Sky is accelerated due to Ed Scriven's death and, knowing that a next-generation version of the Bright Sky satellite is what Odyssey 5 was launching on the day Earth was destroyed, Taggart determines that he must put his career on the line to sabotage the deployment of the current version.

Neil realizes he's falling in love again with his old high school girlfriend, Holly.

Sarah and Angela use their knowledge of the future to try to stop the kidnapping and murder of a young girl, which was front-page news in the original timeline, only to find that their actions have changed the future unpredictably.

Mendel, determining that an organism comprised of the mysterious artificial tissue would be cold-blooded, assembles a thermal imaging system that will distinguish humans from the "Synthetics".

During the surveillance of a suspected Synthetic front, Angela and Kurt engage in a firefight which leaves Kurt in the hospital and Angela abducted by the Synthetics. Following a tip from his old friend and Menthor, Leyton Scott, Chuck learns of a rock, brought back from the moon, that is the link between the Cadre and The Sentients.