Who Is Severus Snape in Harry Potter? His Full Arc, Explained

Snape is the Potions master who picks on Harry in his first lesson, and by the last film he is headmaster of Hogwarts. He was once a Death Eater, and he spends the story working against Lord Voldemort (Ralph Fiennes) while letting Voldemort’s followers believe he is one of them.

Harry cannot see the whole picture. He sees a teacher who humiliates him, resents his father and refuses him affection, and for most of the story Snape shows him nothing else. The memories that explain Snape, at the end, leave all of it intact.

His first rescue gets him blamed for the attack. At Harry’s first Quidditch match, Hermione sees Snape muttering as Harry’s broom tries to throw him off, and sets his robes alight. Professor Quirrell (Ian Hart) later admits that Snape was casting the countercurse, and that the fire broke Quirrell’s own eye contact. Hermione’s accusation is wrong, and her fire still saves Harry. Harry then watches Snape pin Quirrell to a wall and takes it as proof that Snape wants the Stone, while Snape is pursuing the threat Harry has mistaken him for.

Snape’s contempt for a fraud comes with a useful lesson in Chamber of Secrets. His Expelliarmus at the Duelling Club sends Gilderoy Lockhart (Kenneth Branagh) flying, and Harry later uses that spell against Voldemort, including in their final duel. In Prisoner of Azkaban, covering a lesson for Remus Lupin (David Thewlis), he calls Hermione an “insufferable know-it-all” for answering out of turn. Snape is the strict parent here, insisting that Hermione follow the classroom rules even when she knows the answer. His werewolf essay is how she works out what Lupin is, and when Lupin transforms, Snape steps in front of the trio and spreads his arms across them, after Harry has knocked him out.

In Goblet of Fire, Snape blames Harry for raiding his stores, then supplies the Veritaserum, a truth potion, that Dumbledore uses on the false Alastor Moody (Brendan Gleeson). As Barty Crouch Jr (David Tennant) is exposed, the look between Harry and Snape is funny, because Harry was not the thief.

In Order of the Phoenix, Snape teaches Harry to defend his mind, though neither can put their resentment aside. The lessons end when Harry turns Snape’s spell back on him and sees his father bullying the schoolboy Snape, and the lessons stop before Harry can keep Voldemort out. Snape tells Dolores Umbridge (Imelda Staunton) that she has used up his truth potion, the last of it on Cho Chang (Katie Leung), and answers Harry’s coded warning about Padfoot, his name for Sirius Black (Gary Oldman), with “No idea.” What Snape does next happens off screen. In the book (chapter 37), he checks that Sirius is safe and alerts the Order.

Harry trusts a version of Snape with no name attached. The notes in a second-hand Potions book get him a perfect Draught of Living Death and a vial of Felix Felicis, a luck potion, from Horace Slughorn (Jim Broadbent), who later greets him as “the Prince of Potions himself”. Harry drinks the Felix to get the memory about Horcruxes that Slughorn has been hiding, so a potion won with Snape’s notes gets Dumbledore what he needs. The book reaches Harry by chance, and none of this is a gift from Snape.

The same margins hold Sectumsempra. Harry uses it on Draco Malfoy (Tom Felton) in a bathroom without knowing what it does, and Snape has to heal the wounds his own spell made. One perfect potion was a poor reason to trust every spell in the margins.

Snape’s mother was a witch called Eileen Prince, and his father, Tobias Snape, was a Muggle. Prince is a surname, and half-blood describes his parents, so Snape made himself a title out of his mother’s side of the family. In Half-Blood Prince, chapter 30, “The White Tomb”, Hermione Granger (Emma Watson) finds the trail in old copies of the Daily Prophet, where one notice records the marriage and a later one announces the birth of their son.

On screen, Harry hears the declaration and nothing else. Every other Harry Potter title is explained in its own film, and this one needed a single extra fact that never arrives. Keeping that fact in the book is a frustrating choice for a film named after it.

After Dumbledore’s death, Harry chases Snape across the grounds. When Bellatrix Lestrange (Helena Bonham Carter) knocks Harry down, Snape calls her off: “No! He belongs to the Dark Lord!” Harry has just watched him kill Dumbledore, so he has no reason to hear protection in that command. His last try is Sectumsempra, and Snape knocks him flat: “You dare use my own spells against me?” Harry learns who wrote the notes when he least wants to thank him, as a name shouted at him in the dark: “I’m the Half-Blood Prince.”

In Deathly Hallows Part 1, a silver doe leads Harry to a frozen pool with the Sword of Gryffindor in it. Harry’s own Patronus is a stag, and only the later memories show whose the doe is.

Dumbledore asked him to. In Snape’s memories, Dumbledore is already living with a curse in his blackened hand. Snape’s potion can only hold it there, and he warns, “It will spread, Albus.” Dumbledore asks how long. “Maybe a year.”

Dumbledore starts from Draco’s orders, “We both know Lord Voldemort has ordered the Malfoy boy to murder me,” and then states the arrangement plainly: “You must be the one to kill me, Severus.” The reason follows. “Only then will the Dark Lord trust you completely.” Killing the headmaster keeps Snape’s place inside Voldemort’s circle, at the cost of appearing to destroy the man who relied on him. Dumbledore is asking for a death that is already coming.

Snape has already promised to finish Draco’s task. Narcissa Malfoy (Helen McCrory) asks him to protect her son and, if Draco should fail, to carry out the deed Voldemort ordered Draco to perform, and Snape swears an Unbreakable Vow. Harry knows the price of breaking one, because when he asks, Ron Weasley (Rupert Grint) answers, “You die.”

Draco has mended the Vanishing Cabinet that lets the Death Eaters into the castle, but on the tower he cannot bring himself to kill Dumbledore. Draco succeeds at the invasion and fails at the killing, and the vow and the agreement ask Snape for the same act. Harry watches from below, on Dumbledore’s orders. “Severus... please” sounds like the last appeal of a man who needs saving, and after the memories it sounds like a request to keep a terrible promise. Harry’s anger still makes sense, because Dumbledore has left him looking at a murder while the explanation sits in the murderer’s memory.

In the novel (chapter 33), Dumbledore adds two reasons: sparing Draco’s soul, and sparing himself a death by torture. Snape asks, “And my soul, Dumbledore? Mine?” On screen, Dumbledore gives one reason, Voldemort’s trust.

Dying in the boathouse, Snape gives Harry his memories, and Harry watches them in the Pensieve. They show how long Snape loved Lily Potter (Geraldine Somerville), Harry’s mother, from childhood to the night he found her body. He had begged Dumbledore to protect her, and after her death he worked for Dumbledore as a double agent among the Death Eaters.

The memories also carry an instruction. “A part of Voldemort lives inside him,” Dumbledore says of Harry, and Harry must die at Voldemort’s own hand: “That is essential.” Snape is appalled that Harry has been kept alive to die at the proper moment, and when Dumbledore taunts him, “Don’t tell me now that you’ve grown to care for the boy,” Snape answers with his Patronus, a doe. Dumbledore asks, “Lily? After all this time?” Snape answers, “Always.” His final help explains the protection and sends Harry into the forest.

The heroic reading credits seven years of protection and a double life inside Voldemort’s circle, including the hatred he accepts after Dumbledore’s death. The critical reading refuses to let love for Lily excuse how Snape treats her son and his friends: the humiliation in Potions, “Your father was a swine,” the “insufferable know-it-all”. Both readings accept his courage, and they split over whether it outweighs the cruelty.

Our view: the memories explain the protection and leave the ugliness of his behaviour intact. On screen there is still a reason to distrust him, too. In Deathly Hallows Part 1 he gives Voldemort the real date of Harry’s move from Privet Drive, and Alastor Moody and Hedwig die in the attack that follows. Only the novel explains that decision. In chapter 33, Dumbledore’s portrait tells him to pass the date on, because withholding it would cost him Voldemort’s trust, and to suggest decoys to keep Harry safe.

Voldemort has Nagini kill Snape in the boathouse, because he believes killing Dumbledore made Snape master of the Elder Wand. He is wrong. Draco disarmed Dumbledore on the tower before Snape cast the curse, and the wand’s loyalty went to Draco, so Snape dies for a wand that was never his. He has no ordinary conversation left in which to explain himself to the pupil he spent years alienating, so he hands Harry his memories, and his last words are about Lily, “You have your mother’s eyes.”

Nineteen years later, Harry’s younger son is Albus Severus Potter (Arthur Bowen). Harry tells him that one of the two headmasters he is named after was a Slytherin, and “probably the bravest man I ever knew”. That praise belongs to Harry, who saw everything Snape did, cruelty included.