Chapter 1: The Tomorrow War ending explained
The world is stunned when a group of time travellers arrive from the year 2051 to deliver an urgent message: thirty years in the future, mankind is losing a global war against a deadly alien species.
As outlined in the synopsis, we begin with a war veteran turned high-school science teacher Dan being drafted into the war in the future, being forced to abandon his wife (Betty Gilpin) and daughter. The way time travel works in The Tomorrow War is surprisingly well explained (sorry, Christopher Nolan, no 'just feel it' here).
Effectively, the future has created time travel, but the way it works is as if there are two rafts at different points in a river. You can travel from one raft to the other, but both rafts continue to flow with the current (i.e. time). This puts the kibosh on any time travel to before the aliens began destroying humanity and destroying them first since the 'future' can only ever go back 30 years since they – and the past – are constantly moving forward with the current of time.
In the future, Dan is put into a squad with some other soldiers and they're sent on almost-always-fatal missions to stop the advancing alien army. However, Dan soon meets up with a woman named, surprise, Dr Muri Forester (Yvonne Strahovski).
It turns out she is Dan's daughter, all grown up and trying her best to save the world. What she knows, and what haunts her, is that her dad comes back from the future war as a changed man, and eventually he gets divorced and dies in a car accident when she's still young.
It is against this personal ticking clock that Muri has to also race to save humanity, and potentially save her father. Muri figures out that the female alien is the one in charge, while the males would simply die (and kill) to save her, so they kidnap her to develop a toxin that will kill her, as her body has managed so far to metabolise the toxins they use to kill the weaker males.
Muri develops the toxin but only moments before the female alien breaks free, the lab is inundated by the other aliens come to save their leader. A battle ensues, and Muri – knowing that she has to stay in the 'future' – gives the toxin to Dan and then sacrifices herself so that he can be time travelled back into the present with the toxin to destroy the aliens as soon as they land.
Dan arrives back in the present, clearly disturbed by what he now knows about his own future and, of course, the fate of the world. But he has the toxin.
However, no one can figure out when the aliens arrived. It's then that his wife has the brilliant (if a bit far fetched) epiphany: just because they attacked in 2048 doesn't mean they landed then. He enlists the help of squadmate Lt Hart (Edwin Hodge) who has a claw on a necklace from an alien he killed.
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