Harry Potter: Severus Snape's Relationship With Lily Potter, Explained

By the time the "Harry Potter" books and movies come to a close, we learn something vital about Hogwarts Potions master and secret double agent Severus Snape (who's portrayed as an adult by Alan Rickman in the films). That something is that basically every choice he makes throughout his life is connected, in some way, to his love for Lily Potter.

Lily, as fans of the "Harry Potter" franchise know, is the mother of the titular Harry Potter (Daniel Radcliffe in the original movies), and in the final book, "Harry Potter and the Deathly Hallows," and its two-part film adaptation, we get a look at full flashbacks that tell Snape and Lily's entire story. So, where does it begin?

Snape and Lily become friends because they live near each other; Snape resides on a street called Spinner's End, which is canonically part of a fictional British town called Cokeworth. One day, while Lily and her sister Petunia are playing, they're confronted by a young Snape, who clues Lily into the fact that she has magical abilities and that Hogwarts School of Witchcraft and Wizardry is real. One day, while they're spending time together without Petunia, Lily worries that the magical school might be a trick, but Snape reassures her:

"'It's real for us,' said Snape. 'Not for her. But we'll get the letter, you and me.'
'Really?' whispered Lily.
'Definitely,' said Snape, and even with his poorly cut hair and odd clothes, he struck an oddly impressive figure sprawled in front of her, brimful of confidence in his destiny."

Sadly, Lily and Snape's time at Hogwarts is where their friendship starts to truly fall apart ... and the two choose different paths. So, how does Snape and Lily's relationship evolve in "Harry Potter," and why is it so important?

Some much-needed context: During "Deathly Hallows," Harry, who has always believed that Snape is a villain, watches as the Potions master is murdered by the Dark Lord Voldemort (played by Ralph Fiennes) and Voldemort's massive snake Nagini (one of his Horcruxes). In Snape's final moments, he magically provides Harry with memories that chart Snape's entire history with Lily, beginning with their days in Cokeworth; when they start at Hogwarts in the same year, Snape is disappointed as Lily is sorted into Gryffindor while he finds himself in Slytherin.

From there, the two drift apart ... but the real division happens during a memory that Harry partially sees back in "Harry Potter and the Order of the Phoenix," where Harry's father James and his friends bully Snape. When Lily tries to defend Snape, he calls her a "Mudblood," a slur for Muggleborn witches and wizards. In "Order of the Phoenix," we see Lily's reaction; she calls him "Snivellus," the mean nickname given to him by said bullies, and says she won't bother defending him ever again. Then, in "Deathly Hallows," we see the other side of this memory:

"'I never meant to call you Mudblood, it just —'
'Slipped out?' There was no pity in Lily's voice. 'It's too late. I've made excuses for you for years. None of my friends can understand why I even talk to you. You and your precious Death Eater friends — you see, you don't even deny it!'"

Then Lily delivers a final blow, saying Snape's clearly chosen his way: "But you call everyone of my birth Mudblood, Severus. Why should I be any different?" That's the end of their friendship, but Snape's enduring love for Lily becomes vitally important again years later.

Years after Lily and Snape choose their different paths at Hogwarts, Snape, now a fully committed Death Eater, misunderstands a prophecy that he overhears at Voldemort's behest and gives his boss bad information. As a result, Voldemort goes after James, Lily, and baby Harry ... and though Hogwarts headmaster Albus Dumbledore (Michael Gambon in "Deathly Hallows: Part 2") is disgusted with Snape's actions, he allows him to become a double agent who secretly protects Harry throughout the entire franchise.

So, why does Snape do this, especially because he seems to really hate Harry's guts? That's the question Dumbledore raises in Snape's memory when he tells the Potions master that both Harry and Dumbledore must die. What follows is one of the most famous passages in the entire book series:

"'But this is touching, Severus,' said Dumbledore seriously. 'Have you grown to care for the boy at all?'
'For him?' shouted Snape. 'Expecto Patronum!'
From the tip of his wand burst the silver doe: She landed on the office floor, bounded once across the office, and soared out of the window. Dumbledore watched her fly away, and as her silverly glow faded he turned back to Snape, and his eyes were full of tears.
'After all this time?'
'Always,' said Snape."

Snape's Patronus is a doe to represent Lily, and every single time he risked his life to help Harry was in service of the woman he loved and lost. Lily's love for Harry magically protected him against Voldemort, but without Snape's protection, the kid would have probably been toast ... and that's why Snape and Lily's bond is basically the backbone of the story of "Harry Potter." You can stream the movies on HBO Max and Peacock.