The seventh and final installment in the Harry Potter series opens with a dark scene at the Malfoys', where Voldemort is awaiting Snape's report on Harry's whereabouts. The Dark Lord is back in power, and his reach threatens even those in the Muggle world; at No. 4 Privet Drive, Harry convinces his aunt and uncle to go into hiding. As the family departs, Dudley thanks Harry for saving his life. The Order of Phoenix arrives to escort Harry to safety, but they are attacked by Death Eaters. Harry, Hermione and Ron apparate to the Burrow, home of the Weasleys.

While the Weasleys prepare for Bill and Fleur Delacour's wedding, Harry, Ron and Hermione strategize ways to destroy the five remaining Horcruxes. To their surprise, they discover that Dumbledore, the beloved headmaster of Hogwarts, has left them items in his will: Hermione, a children's book; Ron, a Deluminator; and Harry, Gryffindor's sword and a Golden Snitch. Bill and Fleur's wedding reception is ambushed by Death Eaters, and Harry, Ron and Hermione barely escape. They start on their quest to find the first Horcrux on their list, Salazar Slytherin's locket, and steal the Gryffindor sword from the Ministry of Magic. They find out the sword is a fake, but they manage to steal the locket from Dolores Umbridge.

Forced into hiding, their ultimate destination unknown, the three former Hogwarts students live like nomads, sleeping in a different place every night. Their straitened circumstances lead to frequent quarrels, and one cold day Ron and Harry have an epic fight, which ends with Ron deserting them. Harry and Hermione are crushed but continue their journey. They decide to go to Harry's birth town, Godric's Hollow, in search of clues and inspiration. But they are attacked there by Voldemort's snake, Nagini, who has assumed the shape of the witch historian Bathilda Bagshot (whom Voldemort has killed). They survive, but Harry is devastated when Hermione tells him his wand has been destroyed during the fight.

During their travels, Harry and Hermione also meet Dumbledore's brother and learn the story of their sister. They are surprised to learn that Dumbledore aspired for great power during his youth. Harry is crushed by the new information about his idol. He and Hermione continue to hunt for Gryffindor's sword. One night, in a stupor, Harry is led to a pond where he sees the sword and attempts to claim it. Harry's locket Horcrux tries to choke him, but Ron suddenly appears, saves Harry, and destroys the locket with the sword.

On a hunch, Hermione leads the three to Xeno Lovegood's house, and they learn the story of the three magical talismans that make up the Deathly Hallows: the Elder Wand, a stone that brings back the dead, and the true Invisibility Cloak, which later is revealed to be Harry's cloak. Whoever possesses all three is the Master of Death and gains eternal life. Harry is faced with a tough choice: continue with his original quest to find and destroy the Horcruxes, thus ultimately destroying Voldemort, or chase the Hallows in search of eternal life. But when Harry discovers that Voldemort is in search of the Elder Wand, it becomes clear to him that he must focus on the Horcruxes.

Every night, Harry and his friends are encouraged by the broadcasts on "Potterwatch," a secret radio station for supporters of the boy wizard. Through teamwork, Harry and his friends find two more Horcruxes: a Hufflepuff cup in the Gringott's vault and Ravenclaw's diadem, in search of which they travel back to Hogwarts at last.

At Hogwarts, Harry, Ron and Hermione reunite with the rest of Dumbledore's Army, and a battle erupts. Fred Weasley dies, and the tiara burns in a fire. Ron and Hermione destroy the cup with poisonous Basilik venom. One Horcrux remains: the snake, Nagini.

Reading Voldemort's mind, Harry finds Voldemort in the Shrieking Shack with Severus Snape. Voldemort kills Snape, believing that it will give him the power of the Elder Wand. Before Snape dies, he gives Harry his memories. Harry is surprised to learn that Snape was always loyal to Dumbledore and always loved his mother Lily. Harry realizes that part of Voldemort is inside him, and for Voldemort to die, Harry must die.

Harry confronts Voldemort, and suddenly Harry is with Dumbledore. Dumbledore tells Harry that the piece of Voldemort that lived inside him is dead, and he can either stay or return and fight. Harry chooses to fight. In their final battle, Harry, the true master of the Elder Wand, defeats Voldemort.

The trio heads back to Dumbledore's office, and Harry gives up the Elder Wand. Peace is restored.

An epilogue reveals that Harry's scar has not hurt in 19 years. Ron and Hermione are married. Harry and Ginny are married. They have three children, Lily, James and Albus.