Plot

Half a year into his solo mission on the edge of the solar system, an astronaut concerned with the state of his life back on Earth is helped by an ancient creature he discovers in the bowels of his ship.

An intergalactic odyssey of love, ambition, and self-discovery. Orphaned as a boy, raised in the Czech countryside by his doting grandparents, Jakub Procházka has risen from small-time scientist to become the country's first astronaut. When a dangerous solo mission to Jupiter offers him both the chance at heroism he's dreamt of and a way to atone for his father's sins as a Communist informer, he ventures boldly into the vast unknown. But in so doing, he leaves behind his devoted wife, Lenka, whose love, he realizes too late, he has sacrificed on the altar of his ambitions. Alone in Deep Space, Jakub discovers a possibly imaginary giant alien spider, who becomes his unlikely companion. Over philosophical conversations about the nature of love, life and death, and the deliciousness of hazelnut spread, the pair form an intense and emotional bond.—Bluewater

Czech astronaut Jakub Prochazka (Adam Sandler) is six months (189 days) into a solo space mission to investigate a mysterious cloud of dust and particles, called Chopra, lying beyond Jupiter. The cloud appeared 4 years ago, and Jakub's mission is to collect samples of the cloud and return to Earth. The dust cloud is pink in color and is so vast that it is visible from Earth. The mission is a joint endeavor between the European Space agency and Czech government. Jakub is scheduled to arrive at the cloud in less than a week.

The spacecraft is modular in nature and has a communications module, a central module (that connects to all the others), a toilet module, a sleeping quarter and so on.

The Czech mission has arrived shortly before the South Korean astronauts to the post, being the first to launch to explore Chopra. Jakub struggles with loneliness and misses his wife, Lenka (Carey Mulligan), who has recently stopped talking with him after he left her and their unborn daughter behind to go on the mission. The communication with Earth is instantaneous despite that large distance involved. Jakub is now 500 million kilometers away from Earth. The technology is called the CzechConnect Quantum, which is a phone that communicates at faster than the speed of light.

Lenka sends him a message telling him that she wants to leave him, but Commissioner Tuma (Isabella Rossellini), Jakub's commanding officer, prevents it from reaching him, to prevent Jakub's mental state from worsening. Jakub is already having sleepless nights on the spacecraft and is under increasing stress to meet mission objectives despite the spacecraft not working as designed. Jakub tells Peter that he cannot sleep as the toilet keeps making a noise all night, but Peter says that fixing other parts of the ship are a higher priority. Half the cameras on the ship are malfunctioning.

Jakub tries to call Jenka on CzechConnect, but she ignores his calls (CzechConnect requires a specialized equipment to be installed at home for the technology to work, and the calls can only be taken from inside the CzechConnect console). Jakub asks his daily contact Peter to go and check on Lenka at his home. Peter is Jakub's friend and knew that Lenka was planning to leave him. He tells Jakub that she has just gone to visit her mother and is hence unreachable.

Days later, still without news from Lenka, Jakub finds a spider-like creature with telepathic abilities inside a compartment of the ship. The spider is huge in size and scares Jakub as he had been having nightmares about spiders entering his body through the eye. The Spider says that it was attracted by the meditative sounds coming from Jakub's spacecraft (referring to the noise coming from the toilet). Jakub locks himself in the airlock and releases Decontaminants in the ship, but they do not affect the spider. The spider assures Jakub that he would neither consume nor contaminate him.

The creature, whom Jakub names Hanus (Paul Dano), wishes to understand humans better and to help Jakub with his loneliness. Jakub does reveal the existence of Hanus to Peter or anybody else in mission control. Hanus says that he is an explorer who came to the solar system and felt the pull of humans. He studied Earth from orbit and learned its languages and yet did not understand the human race. Hanus then encountered Jakub's ship travelling through space and came to meet him as Jakub's loneliness intrigued him. Hanus says that he believes that he can help Jakub.

At first Jakub does not trust Hanus and tries to keep away from him as much as possible. He increases his dosage of sleeping drops so at least he can sleep without discomfort. Slowly, Jakub gets used to Hanus's presence. Hanus wants to eat eggs, but Jakub doesn't have any as they don't preserve well. Hanus says that he fled his planet after it was attacked by Gorompeds. He traveled through galaxies and black-holes to reach the Milky Way.

Hanus has the ability to access Jakub's memories, where he learns about Lenka, how they met, their early courtship and so on. Exploring his memories, Hanus learns more about Jakub: his father was an informant of the Communist Party of Czechoslovakia and was killed when Jakub was young. Jakub was being raised by his father to be a pig farmer, but his dreams got bigger after his father's death. He met Lenka, but often neglected her, being more focused on his career as a cosmonaut, going as far as leaving her when she suffered a miscarriage. Hanus is intrigued to understand that Jakub chose to leave his planet and yet space is destructive to him. Hanus understands that Jakub hopes to atone for the sins of his father by completing this great mission successfully. A grain of Chopra cloud enters the spacecraft when it is 45 hours away from the cloud, and Jakub learns that the grain cannot be captured by any material substance. His communications go offline till the grain is inside the spacecraft.

After showing Jakub an implanted memory of the miscarriage, which Jakub was not present for, Hanus, disappointed with humanity (Jakub still did not return home to Lenka after she lost their first child), leaves the ship, leaving Jakub distressed.

Jakub arranges with technician and good friend of his, Peter (Kunal Nayyar), to get him to deliver a message to Lenka, asking for forgiveness for his neglect. Hanus returns after this, revealing that he's dying due to a parasitic infection that wiped out his entire species.

The two finally arrive at the Chopra cloud, which is revealed to be a leftover of the beginning of the universe and where every moment of time exists simultaneously. Hanus leaves to die in space, but Jakub goes after him. Within the cloud, Jakub comes to the conclusion that he only wishes to be with his wife. Hanus passes away due to the infection.

Jakub is picked up the South Korean space vessel. Jakub and Lenka talk again, coming to terms with their relationship.