In the year 2073 Nicholas Sinclair is a scientist on a time travel project. An accident introduces a deadly virus in to the past in 1973, causing a paradox. The project’s automatic countermeasures activate and attack robots are sent in to the past to try to eliminate the virus carriers. They fail to contain the virus, and Sinclair returns to 2073 to find the Earth in ruins, ravaged by both the virus and the attack robots continually sent from the original timeline. Sinclair travels to the ruined project lab in the paradox timeline and uses the equipment there to travel to the original timeline and prevent the mission that caused the paradox, resolving it.