Five strangers come together when a team of secret operatives from the future transmit their conscious minds back into the past, taking over people's bodies at the moment of their death.
With the team assembled in the present day they prevent a catastrophic antimatter explosion, but run into trouble when they must hand over the device to another team of Travelers. The agent who has become Grant MacLaren meets his wife, while Marcy seeks to prove herself to David -- and Philip experiences difficult withdrawal symptoms.
Frustrated by a lack of action Philip acts to prevent the death of an innocent boy, sending the Travelers off-mission. Meanwhile Philip reaches out the parents of the young man he allowed to die.
Following a shoot-out MacLaren's team is called to assist a team of injured fellow travelers, provoking a challenge to his leadership. Carly's ex Jeff puts pressure on both her and Marcy, and Trevor reckons with his future when the school guidance counselor calls him in to a meeting.
The team is abducted and interrogated by a mysterious figure who knows something about their real identity as Travelers, leaving MacLaren on his own to try and find them after David reports Marcy's disappearance.
The team draws near their primary mission: to use Dr. Delaney's anti-matter device to deflect an asteroid that will alter the course of human history. But as the team prepares to put their lives on the line, Major Gleason takes Delaney into custody.
Believing they have successfully completed their mission in the past the team prepares to live out the remainder of their lives in the twenty-first century. But each one begins to experience hallucinations as a side-effect from the anti-toxin injections.
The arrival of a new team goes horribly wrong when the Traveler sent to replace a bomber fails to stop the explosion. Marcy tries to intervene when David's boss questions his actions, and Carly squares off against her ex in court.
MacLaren receives a mysterious assignment that seats him on an airliner next to a U.S. Senator. Meanwhile Trevor tries to mend fences with his father, and David tells Marcy that she has to move out.
As a team of doctors from the future work to save his life MacLaren experiences memories of his host's life with Kat. As Philip tries to cover up Mac's involvement in the plane crash, Kat and his partner Forbes grow suspicious.
As the team prepares for the arrival of high-ranking Traveler 0014, Marcy finds herself hospitalized with her time running out. Meanwhile Trevor defies the Director by abducting his guidance counselor in order to save her life, and Carly runs into new trouble with her domestic issues.
A rogue faction sends an assassin back in time to kill Grace, who reveals a profound new problem with the Director in the future. David attempts to adjust to Marcy's change, and MacLaren's team also find themselves targets of enemy agents.
