In the 22nd century, rising sea levels from global warming
have wiped out coastal cities and altered the world's climate.
With the human population in decline, nations have created
humanoid robots called mechas to fulfill various roles.

In Madison, New Jersey, David, an 11-year-old prototype mecha
child capable of love, is given to Henry Swinton and his wife
Monica, whose son Martin is in suspended animation. Monica
initially feels uncomfortable but warms to David after he is
activated and imprinted. David befriends Teddy, Martin's robotic
teddy bear.

After Martin is cured and brought home, he goads David into
cutting off a piece of Monica's hair. Later, David accidentally
pokes Monica's eye with scissors. During a pool party, David
reacts to being poked with a knife and both he and Martin fall
into the pool. Martin is saved, but David is blamed.

Henry convinces Monica to return David to his creators for
destruction, but instead, she abandons him in the woods with
Teddy. David, believing that becoming human will regain Monica's
love, decides to find the Blue Fairy.

David and Teddy are captured by the "Flesh Fair", where obsolete
mechas are destroyed. David pleads for his life, and the audience
allows him to escape with Gigolo Joe, a mecha framed for murder.
They travel to Rouge City, where "Dr. Know", a holographic answer
engine, directs them to the ruins of New York City and suggests
that the Blue Fairy may help.

David meets Professor Hobby, who shows him copies of himself,
including female variants. Disheartened, David attempts suicide,
but Joe rescues him. They find the Blue Fairy, which turns out
to be a statue. David repeatedly asks the statue to turn him
into a real boy until his power source is depleted.

Two thousand years later, humanity is extinct and Manhattan is
buried under ice. Mechas have evolved, and a group called the
Specialists resurrect David and Teddy. They reconstruct the Swinton
home from David's memories and explain that he cannot become human.
However, they recreate Monica using genetic material from the
strand of hair Teddy kept. Monica can live for only one day.

David spends his happiest day with Monica, and as she falls asleep,
she tells him she has always loved him. David lies down next to her
and closes his eyes.