Planet Earth, Pleistocene, savannahs of equatorial Africa.

A small tribe of Pithecanthropus is on the verge of extinction. Nature did not endow them with powerful fangs, nor sharp claws, nor fast legs, but glimpses of consciousness flickered in their eyes. Probably these very qualities attracted the attention of some highly developed extraterrestrial civilization, which carefully cultivates the seeds of the Mind wherever they can be found. Pithecanthropus become experimental in a grand space experiment.

One night a block of completely transparent material appears in a river valley. At dusk, when the tribe returns to the caves, an unusual stone suddenly makes a strange vibrating sound that attracts the Pithecanthropus like a magnet. In the thickening darkness, the crystal comes to life, begins to glow, bizarre drawings appear in its depths. Enchanted Pithecanthropus do not know that during these moments the device examines their brain, evaluates their abilities, predicts possible directions of evolution. The crystal calls to itself one or the other, and they, in addition to their will, make new movements: naughty fingers tie the first knot on Earth, the leader picks up a stone in his hands and tries to hit the target. Lessons continue every night. Over the year, the life of the tribe changes beyond recognition - now Pithecanthropus can use a set of simple tools, hunt large animals. Eternal hunger and fear of predators recede into the past, there is time for the work of thought and imagination. The mysterious monolith disappears as suddenly as it appeared. His mission is accomplished - an animal endowed with intelligence has appeared on Earth.

XXI century American researchers find on the moon, already inhabited by humanity, the first irrefutable evidence of the existence of an extraterrestrial civilization.

As the chairman of the National Council on Astronautics urgently called to the moon finds out, magnetic reconnaissance has detected a powerful distortion of the magnetic field in the vicinity of the Tycho crater, and excavations in the center of the anomaly have found a parallelepiped of ideal proportions from unknown on Earth heavy-duty black matter at a depth of six meters. The most striking thing about this find is its age: geological analysis suggests that the monolith was buried here about three million years ago.

When the moonlight dawns and the black monolith catches a ray of sunshine for the first time after three million years of imprisonment, a piercing electronic cry is heard in the headsets of people standing around. This signal is detected by space monitors and probes, and the central computer, after processing the information, concludes: a directed energy pulse, obviously of artificial origin, rushed from the moon's surface in the direction of Saturn.

All this is known only to a handful of people, for the consequences of the shock that humanity will inevitably have to endure are unpredictable.

Interplanetary space. Discovery Spaceship. The first months of the flight pass in serene calm. Two awake crew members - Frank Poole and David Bowman - are on guard duty daily. The other three are immersed in an artificial hypothermic dream, from which they will only be awakened when the Discovery enters the orbit of Saturn. Only these three are aware of the true purpose of the expedition - a possible contact with extraterrestrial civilization, while Poole and Bowman consider flying a regular research trip. Those who prepared the expedition decided that it was necessary for the Security and Interests of the nation.

In fact, the ship is not controlled by people, but by the sixth crew member, Eal - the Discovery brain and nervous system, a heuristically programmed algorithmic computer. Eal created through a process similar to the development of the human brain can rightly be called a truly thinking machine, and it speaks to people in a real, figurative human language. All the capabilities of the EAL are aimed at fulfilling the given program of the expedition, but the contradiction between the goal and the need to hide it from fellow human beings gradually destroys the integrity of his “psyche”. The machine starts to make mistakes, and finally a crisis sets in: hearing astronauts talk with Earth about the need to turn off the EAL and transfer control to the Center, he makes the only possible decision: to get rid of people and complete the expedition on his own. He imitates an antenna accident, and when Frank Pool goes into outer space to replace the block, the EAL kills him: a jet capsule-dinghy at full speed flies to the astronaut. And the next moment, the stunned Bowman sees on the screen that the boat is leaving the ship, dragging the body of a deceased friend along with it on the safety cable. Frank Poole the first of the people will go to Saturn.

Bowman is trying to wake one of the sleeping people, but he hears a sound that makes his heart go cold: the doors of the outer hatch open and air from the ship rushes into the abyss of space. He manages to escape in an emergency chamber, put on a spacesuit and disconnect the higher centers of the electronic brain. He remains alone in millions of kilometers from Earth. But the ship’s engines and navigation systems are in good condition, communications with the Earth have been restored, and the emergency supply of oxygen will last for months. The expedition continues, and Bowman, who is now aware of her ultimate goal, reaches the giant dead Saturn. He was ordered to begin the survey of the system from the eighth satellite of Saturn, Iapetus. The entire surface of Iapetus, devoid of atmosphere, is black, reminiscent of charcoal in structure - except for a white plateau of a strikingly regular oval shape with a black mark in the center, which turns out to be exactly the same black monolith as on The moon, only gigantic sizes.

The experiment, begun three million years ago, has ended. The monolith in Iapetus - the Guardian of the Stargate - was installed by the same creatures, who were not at all like humans, who sent a mysterious crystal to Earth and buried a black block on the Moon. Their efforts were not in vain: the Earth really gave rise to Reason, capable of reaching other planets, and the signal of the lunar monolith, which sent news to Iapet, was confirmation of this.

David Bowman decides to sit on Iapetus in a capsule, and her approach awakens the forces contained in Stargate. The upper face of the black monolith suddenly goes deep, the capsule begins to fall into the bottomless shaft. This opened the Stargate.

Time stops - the clock stops counting seconds - but perception and consciousness continue to work. Bowman sees the black walls of the “mine”, and in the lumen of a myriad of stars “scattering” from the center. He realizes that with time and space something is happening that is inaccessible to his understanding, but does not feel fear, feeling that he is under the protection of an infinitely powerful Reason. In the end, he finds himself hundreds of light years from Earth. The capsule strives for a giant red star, into the realm of flame, but when the journey ends, Bowman thinks he's crazy - he's in an ordinary earthly hotel. Only after some time, he realizes that all this is a decoration made by the hosts for the guest on the television movie two years ago. Bowman goes to bed and falls asleep - for the last time in his life. It merges with the cosmic mind, losing its physical body, acquires the ability to move in time and space with the help of thought, and saves the home planet from an impending nuclear disaster.