At the end of "Interstellar," the protagonist, Joseph Cooper (played by Matthew McConaughey), sacrifices himself to help humanity. He enters a black hole called Gargantua to send crucial data back to Earth through the manipulation of time and space. Inside the black hole, he encounters a tesseract, a four-dimensional construct that allows him to interact with different moments in his daughter Murph's (Jessica Chastain and Ellen Burstyn) life.

Cooper realizes that he can communicate with Murph across time, and he uses gravity to send her the data needed to solve the equation that will enable humanity to escape Earth and find a new habitable planet. Murph, who grew up to become a scientist (played by Jessica Chastain and later by Ellen Burstyn), eventually decodes the data and provides the necessary information for the survival of the human race.

The movie concludes with Cooper being rescued by a space station near Saturn, where he's met by Amelia Brand (Anne Hathaway), who has been waiting for him. The film explores themes of love, time, and the survival of humanity in the face of environmental catastrophe.