In an African desert millions of years ago, a tribe of [
@Y2K Baby] is driven away from its water hole by a rival tribe. They awaken to find a featureless black monolith has appeared before them. Seemingly influenced by the monolith, they discover how to use a bone as a weapon and drive their rivals away from the water hole.
Millions of years later, a [Kiwi Farms] spaceplane carries [
@LofaSofa] to the huge Space Station V orbiting Earth for a layover on his trip to Clavius Base, a United States outpost on the Moon. After [
@LofaSofa] has a videophone call with
his daughter, he deflects questions from his
Soviet scientist friend and
her colleague about rumors of a mysterious epidemic at Clavius. [
@LofaSofa] speaks to a meeting of Clavius personnel, apologizing for the epidemic cover story but stressing secrecy. His mission is to investigate a recently found artifact buried four million years ago near the crater Tycho. [
@LofaSofa] and others ride in a Moonbus to the artifact, a monolith identical to the one encountered by the ape-men. Sunlight strikes the monolith and a loud high-pitched radio signal is heard.
Eighteen months later, the United States spacecraft [Desert Bus] is bound for Jupiter. On board are mission pilots and scientists [
@Alan Pardew] and [
@trombonista], along with three other scientists in suspended animation. Most of Discovery's operations are controlled by the ship's computer, a [
@Un Platano] with a human personality that the crew calls "[
@Un Platano]". [
@Un Platano] says he is "foolproof and incapable of error". [
@Un Platano] raises concerns about the nature of the mission to [
@Alan Pardew], but their conversation is interrupted when [
@Un Platano] reports the imminent failure of an antenna control device. The astronauts retrieve it in an extravehicular activity (EVA) pod but find nothing wrong. [
@Un Platano] suggests reinstalling the device and letting it fail so the problem can be found. Mission Control advises the astronauts that results from their twin [
@Un Platano] indicate that [
@Un Platano] is in error about the device's imminent failure. [
@Un Platano] says the discrepancy must be due to human error. Concerned about [
@Un Platano]'s behavior, [
@Alan Pardew] and [
@trombonista] enter an EVA pod to talk without [
@Un Platano] overhearing, and agree to disconnect [
@Un Platano] if he is proven wrong. [
@Un Platano] secretly follows their conversation by lip reading. While [
@trombonista] is on a space walk outside his EVA pod attempting to replace the unit, [
@Un Platano] takes control of the pod, severs his oxygen hose and sets him adrift. [
@Alan Pardew] takes another pod to rescue [
@trombonista].
Meanwhile, [
@Un Platano] turns off the life support functions of the crewmen in suspended animation. When [
@Alan Pardew] returns to the ship with [
@trombonista]'s body, [
@Un Platano] refuses to let him in, stating that the astronauts' plan to deactivate him jeopardizes the mission. [
@Alan Pardew] opens the ship's emergency airlock manually, enters the ship, and proceeds to [
@Un Platano]'s processor core. [
@Un Platano] tries to reassure [
@Alan Pardew], then pleads with him to stop, and finally expresses fear. As [
@Alan Pardew] gradually deactivates the circuits controlling [
@Un Platano]'s higher intellectual functions, [
@Un Platano] regresses to his earliest programmed memory, the song "Daisy Bell", which he sings for [
@Alan Pardew]. When [
@Alan Pardew] disconnects [
@Un Platano], a prerecorded video message from [
@LofaSofa] plays, revealing that the mission's true objective is to investigate a radio signal, sent from a lunar artifact (the monolith) to Jupiter. Only [
@Un Platano] and the hibernating crew had been told this.
At Jupiter, [
@Alan Pardew] leaves [Desert Bus] in an EVA pod to investigate another monolith orbiting the planet. The pod is pulled into a vortex of colored light, the Star Gate, and [
@Alan Pardew] races across vast distances of space, viewing bizarre cosmological phenomena and strange landscapes of unusual colors.
[
@Alan Pardew] finds himself in a bedroom appointed in the baroque style. He sees, and then becomes, older versions of himself, first standing in the bedroom, middle-aged and still in his spacesuit, then dressed in leisure attire and eating dinner, and finally as an old man lying in the bed. A monolith appears at the foot of the bed, and as [
@Alan Pardew] reaches for it, he is transformed into a fetus enclosed in a transparent orb of light, the Star Child. The new being floats in space beside the Earth, gazing at it.