Forbidden Planet - Plot

Plot

Early in the 23rd century, the United Planets Cruiser C57-D travels to the planet Altair IV, 16 light-years from Earth, to discover the fate of an expedition sent 20 years earlier. Soon after entering orbit, the cruiser receives a transmission from Dr. Edward Morbius, the expedition's linguist. He warns them to stay away, since he cannot guarantee their safety and that he needs no assistance. The starship's captain, Commander John J. Adams, insists on landing anyway.

They are met by Robby the Robot, who takes Adams, Lieutenant Jerry Farman, and Lieutenant "Doc" Ostrow to Morbius's home. There, Morbius explains that an unknown "planetary force" killed nearly everyone and vaporized their starship as the survivors tried to flee the planet. Only Morbius, his wife (who later died of natural causes), and their daughter Altaira were somehow immune to this force. Morbius fears that the C57-D and its crew will meet the same fate. Altaira is fascinated to meet other men after only knowing her father her entire life.

Later the next night, equipment aboard the C57-D is sabotaged, though the sentries never spotted an intruder. Adams and Ostrow visit Morbius the following morning and learn that he has been studying the Krell, a highly advanced native species. The Krell mysteriously all died at once, 200,000 years before, just as they achieved their crowning scientific triumph.

In a still functioning Krell laboratory, Morbius shows Adams and Ostrow a device he calls the "plastic educator," a machine capable of enhancing intellectual capacity; it displays three-dimensional thought projections. The Bellerophon's captain tried using the machine and was instantly killed. When Morbius first used the machine he barely survived, but also found his intellect had been doubled. The increased intelligence, along with information from a Krell "library," enabled him to build Robby and the other technological advances in his house. Morbius then takes them on a tour of a vast cube-shaped underground Krell complex, 20 miles on a side and powered by 9,200 thermonuclear reactors.

In response to the sabotage, Adams orders a defensive force field fence to be deployed around the ship. This proves useless when the intruder returns undetected and murders Chief Engineer Quinn. Dr. Ostrow is confused by a casting made from one of the large footprints the intruder left behind; its features appear to violate all known evolutionary laws.

When the intruder returns again, the C57-Ds crew discovers it is invisible, though its shape is outlined by the energy from the force field fence and any weapons fired at it, though they have no effect. Several of the crew are killed, including Farman. At the same moment Morbius is awakened from a nightmare while in the Krell laboratory by Altaira's screaming, while back at the ship the creature immediately vanishes.

Later, while Adams distracts Morbius, Ostrow sneaks away to use the educator, and he is severely injured. Just before he dies, Ostrow explains to Adams that the underground installation was built to materialize any object the Krell could imagine and send it anywhere on the planet. However, Ostrow realizes the Krell had forgot one thing: "Monsters from the id! Monsters from the subconscious." When confronted by Adams, Morbius objects, pointing out that there are no Krell left. Adams points out that Morbius's mind – expanded by the "plastic educator" – recreated the same creature that killed the original expedition, but Morbius refuses to believe it.

When Altaira declares her love for Adams in defiance of her father's wishes, the monster approaches the house. Morbius commands Robby to kill it, but the robot knows the creature is an extension of his master. The conflict with his programming to never harm humans forces him to deactivate. The monster attacks and eventually melts down the indestructible doors of the Krell laboratory where Adams, Altaira, and Morbius are hiding.

Morbius finally accepts the truth: The creature is an extension of his own mind, "his evil self". He is fatally injured trying to drive the creature away, and the monster disappears. Morbius directs Adams to activate a self-destruct mechanism; he warns them that they must be 100 million miles away within 24 hours. From deep space, Adams, Altaira, Robby, and the rest of the crew witness the destruction of the star Altair and its entire planetary system.