No child has been born for 18 years.
Why it is hard sci-fi
Set in 2027 in a Britain that has sealed its borders after eighteen years of total human infertility. The film never explains the cause, which is a deliberate choice. It treats infertility as a fact and follows the second-order consequences. Detention camps, refugee policy, terminal-age care, decay of public services. Cuaron stages it like reportage.
Science inside it
Reproductive failure as the engine of every other systemic collapse. The biology is left blank on purpose. What the film models carefully is demography. A society without children loses motivation, then loses institutions, then loses cohesion. The order matters.
Spoiler alert
Kee, an African refugee, is pregnant with the first baby in eighteen years. The film ends with her on a small boat in the English Channel waiting for the Tomorrow, a research vessel from the Human Project, while the rebellion that was supposed to protect her dissolves into a militia coup. Theo dies before the rendezvous.