In the year 2063, as Earth grapples with the devastating effects of climate change, a group of astrophysicists uncovers a promising habitable planet. Due to the daunting 86-year journey, it is determined that the original crew will not reach the destination — instead, their grandchildren will complete the mission. To prepare for this, the initial crew of thirty is created through IVF and kept separate from the outside world, ensuring they are equipped to face the long voyage ahead.
The mission is set aboard the Humanitas spaceship, where they launch as pre-teens, under the guidance of the senior program commander, Richard. To manage the inherent challenges of living in space, a dubious plan emerges: at the age of 24, the crew members will undergo IVF again to continue the lineage. However, during their tenth year in space, Christopher and Zac make a shocking discovery — the teenagers' food contains a blue additive designed to repress sexual urges and maintain compliance.
As the two boys reject this chemical, their desires intensify, leading to reckless behavior, including crushes on fellow crew member Sela, the chief medical officer. Tragedy strikes when Richard is mysteriously killed during a spacewalk. Following his death, Christopher is unexpectedly appointed as the new leader, much to Zac's dissatisfaction. In a bid for power, Zac instigates a rebellion, claiming that an alien presence is responsible for the catastrophe.
Zac’s manipulation leads to chaos within the ranks, where he falsely convinces many that he alone can protect them amidst hysteria. In a shocking twist, Christopher and Sela uncover evidence that Zac was responsible for Richard’s demise. Despite revealing the truth, Zac’s control grows as paranoia spreads, resulting in vigilante justice against anyone he deems suspicious.
The situation worsens when Christopher, in a moment of desperation, guides Zac to a stash of weapons intended for their grandchildren once they reach the new world. Cornered, Christopher and Sela — who have formed a bond — manage to outsmart Zac, resulting in his ejection into space, restoring some semblance of order aboard the ship. With Phoebe lost in the turmoil, only Christopher and Sela remain steadfast against the chaos.
In the aftermath, peace is re-established, and Sela is elected as the new chief officer. The crew collectively decides to abandon the blue chemical, embracing their natural emotions and relationships, including the prospect of love and family without the previous constraints of IVF.
Decades pass, and finally, the generations aboard the Humanitas arrive at the long-anticipated planet. From orbit, it reveals itself to possess all the qualities of a new Earth, fulfilling the hopes and dreams of the crew who sacrificed so much to get there.
