NOTE: This spoiler was submitted by Jeremy
An old woman, Murph (Ellen Burstyn), addresses the camera and says her father was a farmer, like almost everybody else was at the time, but he did not start off this way. Her father, Cooper (Matthew McConaughey), was a pilot, as we see him in a craft of his own. We also see Murph as a child (Mackenzie Foy) going into Cooper's room, asking him if he was dreaming about a crash. Murph thinks there is a ghost in the house, which Cooper doesn't believe in.
We see clips of elderly people talking about the area they lived in, which was made up of crops and corn fields.
Cooper also lives with his 15-year-old son Tom (Timothee Chalamet) and father-in-law Donald (John Lithgow). Murph brings in a piece of Cooper's craft to the table during breakfast.
Cooper drives the kids to school to drop them off but also to meet with Murph's teacher. He lets Murph handle the truck, and they end up getting a flat tire on the road. Tom teases Murph and calls her "Murphy's Law". Cooper gets out to change the tire when a drone flies overhead. He hops back in the truck and drives through the corn field to chase after it. They follow it toward the edge of a hill near a lake. Cooper then gets out a device that controls the drone, which he lets Murph try out.
Cooper meets with the kids' school principal (David Oyelowo) and Murph's teacher Ms. Kelly (Collette Wolfe). The principal shows Cooper Tom's test grades and says he'll make a great farmer, though Cooper says Tom could make a great engineer, even if the results don't seem to suggest this. Ms. Kelly shows Cooper a textbook that Murph brought in to show the other kids. This federal textbook is forbidden in the school since they use textbooks that say the Apollo missions were faked to bankrupt the Soviets. Cooper isn't happy with what his daughter is being taught and he mentions that if his wife hadn't passed away, she would be there and would be more calm about this. Murph ends up getting suspended.
Cooper is called home to find a bunch of tractors around the crops. There appears to be something wrong with the food supply.
The next day, the family goes to a baseball game. Donald complains that they serve popcorn at the place instead of hot dogs. The crowd then sees that a huge dust storm is happening. Cooper drives the family home with protective masks. Murph realizes the window in her room is open, so she and Cooper run upstairs to shut it. On the floor are thick and thin parallel lines across the floor made out in dust. Cooper analyzes them and determines they are coordinates.
Cooper drives to the facility that the coordinates lead to, with Murph stowing away in the truck. He gets out bolt cutters to go through the fence, only for a robot, TARS (Bill Irwin), to show up and apprehend Cooper.
Cooper is interrogated by TARS until Dr. Amelia Brand (Anne Hathaway) comes in. She brings Cooper to a room with other scientists, with Murph sitting among them. Leading the group is Amelia's father, Professor Brand (Michael Caine), along with fellow scientists Doyle (Wes Bentley) and Romilly (David Gyasi). They identify themselves as being part of NASA. Professor Brand explains the situation, which is that the Earth's crops and food supply are slowly dying off, and the planned mission is to find a new home in the universe to sustain human life, as there may be no hope to save the planet. Several astronauts before them, led by the famed Dr. Mann, went on what are called the Lazarus Missions prior to the rest of the group to find a new world.
Romilly explains that a wormhole has been discovered that can lead them to a new galaxy with a chance to explore a new world for human life. This is their Plan A. Plan B would involve rebuilding life through fertilized embryos that would replace human life. Cooper disagrees with this plan, so he agrees to Plan A. Murph is not happy with him and she storms up to her room when they get home.
Cooper tries to comfort Murph in her room, but she is too angry to listen. She says that she deciphered a message from the books falling off her shelf in Morse code that says "Stay". Cooper promises to return home, though he doesn't know when. He gives Murph his watch but she throws it against her bookshelf. Before Cooper leaves, a couple of books fall off the shelf.
Cooper drives to the station in his truck as Donald and Tom see him off. Murph is too late to say goodbye. Cooper looks in the passenger seat in the hope that Murph possibly stowed away again, but she is not there. His eyes fill up with tears.
Cooper, Amelia, Doyle, and Romilly blast off into space to begin their mission to Mars and then Saturn, along with TARS and the ship's computer CASE (Josh Stewart). They dock their shuttle onto the space module Endurance. Romilly and Doyle put themselves in hypersleep.
Back on Earth, Professor Brand brings Cooper's truck back for Tom to use. He also tells Donald and Murph that they can send messages that will be transmitted to Cooper, but Murph is still mad.
The astronauts soar through the wormhole, passing through the cosmos and stars and infinite space. They know that time passes differently for them on these planets due to the different gravitational pull. One hour out there amounts to bout seven years on Earth. Taking that into account, Cooper knows that it's crucial that they find a way to complete the mission without wasting what could be a decade for the people on Earth. He makes a plan to go around the black hole Gargantua to what he and the others refer to as "Miller's planet", after another astronaut (Miller) landed on it.
The team lands on Miller's planet, which is set upon a seemingly endless body of water. Romilly stays in the craft while Cooper, Amelia, Doyle, and TARS set out. They find a wrecked beacon in the water, belonging to Miller, whose body is nowhere to be found. From the distance, Amelia thinks she sees mountains, when it is actually a colossal wave headed toward them. Amelia tries to salvage the beacon as Cooper orders her to return to the craft. Doyle is killed by a wave of water while the others make it back inside. There, Romilly has aged 23 years. Amelia realizes that Miller was probably there hours ago and died minutes before they got to the planet.
There is also a number of video messages in the craft that were sent to Cooper. Most of them are from Tom. It starts with Tom in his current age saying that he misses his dad and that he's met a girl named Lois. The messages then show Tom as an adult (now played by Casey Affleck). He has married Lois (Leah Cairns) and they have a baby named Jesse. Cooper is overwhelmed with emotion and he starts crying. Another video message shows Tom looking forlorn, as something has happened to Jesse. He also mentions that Donald has passed away. The last message is from a now adult Murph (now played by Jessica Chastain). She is at the age when Cooper left and promised to return. She starts to weep, making Cooper even more emotional.
Presently, Murph is working with Brand at NASA to finish the equation he's been working on that would figure out how humans can escape Earth's gravitational pull. She still harbors some resentment toward her father for leaving her.
Cooper, Amelia, and Romilly are sitting together trying to figure out which planet they should head to next, Edmunds or Mann. From their discussion, Cooper learns that Amelia is in love with a fellow scientist named Wolf Edmunds, for whom one of the planets is named after. She hopes to be able to see him again soon, and she states that love is the one thing that transcends time and space.
Murph goes to the hospital where her partner Getty (Topher Grace) directs her to Brand's room. He is dying. When Murph expresses hope for the mission's success, Brand admits that he solved his equation long ago but was missing data from a singularity behind a black hole for it to be complete, so he puts what little faith he has left in Plan B. With his dying breaths, he crushes Murph's hope. After he passes, Murph sends a video message to Amelia to inform her of her father's death.
The astronauts come across an icy planet with frozen clouds. There is another craft on the surface with a pod inside. Another person is in hypersleep - Dr. Mann (Matt Damon). He awakens and sees Cooper, and he gets overwhelmed to see another human again, bringing him to cry in Cooper's arms. Afterwards, Mann explains the environment of the planet to the team, stating there there are 67 hours in the day, and another 67 at night, as well as the icy conditions. The team then receives Murph's message to Amelia, which also addresses Cooper. Murph asks if both Cooper and Amelia knew that the mission was a sham and that Cooper simply abandoned his family. Amelia is just as shocked to hear this, and Mann admits that he has considered the mission to be a failure. Amelia begins to cry.
Murph has dinner at the old family home where Tom lives with his family. He and Lois have another son, Coop (Liam Dickinson). Coop and Lois suffer from a cough that is attributed to the conditions of the area. Tom seems to be ignoring the problem and refuses to take his family out of there.
Cooper and Mann go out to navigate the planet together while Romilly and Amelia stay behind. Here, Mann turns on Cooper and removes his emergency oxygen pack before pushing him over the edge of a hill. It's revealed that he forged data of the viability of the planet so he could be found and saved. Since he has considered Plan A a failure, Mann opts for Plan B, and, knowing that nobody can survive on this planet, he leaves Cooper to die. Cooper fights back, only for Mann to crack Cooper's visor by slamming his head against it. Mann escapes while Cooper tries to contact Amelia for help. Mann ends up killing Romilly by blowing up his station while Amelia rushes to Cooper's aid. They pick up TARS and fly after Mann.
Getty tries to help Coop with his cough, but Tom doesn't want his or Murph's help, and he punches Getty in the face. He and Murph leave, following other vans that are evacuating the area as another dust storm starts forming. Murph then drives into the corn fields and douses it with gas before lighting it up with a flare to persuade Tom and his family to leave.
Cooper and Amelia find Mann trying to dock his shuttle with Endurance in space, but he cannot as he hasn't secured the airlock. Amelia tries warning him that the shuttle will depressurize, but it is too late, as the shuttle does just that, causing an explosion that kills Mann.
Cooper manages to get Endurance back under control with the help of TARS. He and Amelia then plan to use the robot to to gather data on the singularity behind Gargantua, and then chart a course to Edmunds' planet. Knowing that they have a limited energy and oxygen supply with them, Cooper and Amelia try to make it home carefully. However, Cooper separates himself from Amelia to let her go on without him. Cooper ends up falling through what looks like another wormhole. It puts him in an odd dimension of sorts. He hears the voice of TARS speaking to him. Cooper floats against what looks like a wall. He peeks through it and sees Murph as a child. He is looking at her through her bookcase. Cooper calls out to her and starts pushing the books. TARS explains that he has stumbled upon a new dimension relative to time, space, and gravity, and that the beings that invented this dimension led Cooper to find this place. They know humans could not have created this just yet, but soon enough. Cooper sees himself on the day that he left Murph, and he yells at himself to stay. He notices the watch he left Murph sitting on the bookshelf, and he taps his fingers against the lining of the dimension to try and communicate with Adult Murph through the hands on the watch. Adult Murph is still trying to get Tom's family out of the house while the fire in the corn fields is being extinguished. Now, both Cooper and Murph realize that Cooper was the "ghost" in Murph's room - he was the one that left the message in Morse code for Murph that read "Stay". Adult Murph then figures out that her father is communicating with her. This gives her what she needs to solve Brand's equation and to save mankind. She goes to the research facility, gathers all the papers she once worked on and throws them into the air before excitedly kissing Getty. Cooper, meanwhile, falls through the dimension and drifts through space before blacking out.
Cooper awakens in a medical station. The doctor tells him to relax and take it slow, as he is now 124 years old. Cooper walks to the window and sees kids playing baseball, when the batter hits the ball and it goes through the window of a house - a house that is directly above the playing field. The doctor says they are in Cooper Station over Saturn. Cooper thinks it's named after him, but it's named after Murph. The doctor says she'll be arriving in a few weeks.
Cooper is given the remains of TARS and is brought to his old home. He works on him and reprograms his settings, making him more honest and slightly more humorous.
Cooper gathers with his great grandchildren at the hospital to be reunited with Old Murph as she lying in bed surrounded by her family. She is happy to see her father, who has fulfilled his promise to return to her. Knowing that her time is short, she encourages Cooper to continue living and sharing his life with someone. She tells him to find Amelia, who is lost and setting up camp somewhere out there.
Amelia is shown on Edmunds' planet putting Plan B into effect, trying to rebuild a community with the smaller organisms and unaware of what has happened with humanity. Cooper decides to follow Murph's advice and seek out Amelia himself.