They announce that in November 2048, aliens called White Spikes suddenly appeared in northern Russia and had wiped out most humans within a span of just three years.
The world of the present-day sends their militaries into the future through a wormhole device, but fewer than 30% survive their seven-day deployment, prompting an international draft.
Dan receives a draft notice and is fitted with a temporal armband to track him and pull him back if he is alive at the end of his seven days.
The draftees are sent forward in time to a battlefield on Miami Beach, where their commander orders them to rescue nearby lab personnel before sterilizing the area.
Muri tells Dan there is a toxin that kills male White Spikes, but not the female queens, and asks for his help in capturing a female White Spike to refine the toxin to be fatal to them.
She also tells Dan that in the past, he became disillusioned after failing to get his research job, divorced his wife Emmy, and died in a car crash when Muri was sixteen.
They capture a female White Spike but are attacked by hundreds of males and narrowly escape by helicopter to DEEPSWELL-9, a fortified offshore oil platform 25 miles east of Port Nelson.
Muri succeeds in developing a toxin lethal to female White Spikes, but it cannot be mass-produced in that time period, so she asks Dan to take it into the past to produce it there and prevent the war.
However, the base is overrun by male white spikes in a coordinated effort to protect their queen, causing Muri to sacrifice herself to return Dan to the past.
Dan leads a mission to Russia with Charlie, Dorian, stranded future soldiers, and his estranged father James, a veteran of the Vietnam War.
They find the alien ship frozen in ice beneath the Academy of Sciences Glacier, and surmise that global warming may have freed them in the future.
They then inject the lethal toxin into several White Spikes who have been in a state of hypersleep, but this then awakens the rest of the colony who begin to attack the group.
Queen White Spike eventually awakens as well and escapes. Dorian, terminally ill with cancer, stays behind and blows up the ship while Dan and James pursue the queen.
Content knowing that the war is averted and humanity is saved, Dan brings James home to meet Emmy and Muri, and is determined to avoid the same mistakes that the future Muri warned him about.