Harry, Ron, and Hermione disarm Snape

Harry, Ron, and Hermione disarm Snape in a critical moment inside the Shrieking Shack, an act that derails Snape's plan to hand Sirius Black over to the Dementors and clears the way for the revelation of Peter Pettigrew's survival. The event is a turning point in the climax of the novel, where the three friends, acting on a shared impulse, physically and magically overpower a teacher to protect a man they are only beginning to believe is innocent.

Background and Confrontation

Snape had tracked the group to the Shrieking Shack using the Marauder's Map, which he found in Lupin's office. He arrived just as Lupin and Black were beginning to explain the truth about Pettigrew. Snape, convinced that Lupin was helping Black, immediately attacked, binding Lupin with ropes and preparing to deliver Black to the Dementors. He was beyond reason, his eyes holding a mad glint as he declared, "Vengeance is very sweet" and threatened to call the Dementors to perform the Kiss on Black. Harry, Ron, and Hermione were present, with Ron still clutching the struggling rat that was actually Pettigrew.

The Simultaneous Disarming

As Snape prepared to drag the bound Lupin and the captive Black out of the shack, Harry stepped forward to block the door. Snape, furious, shouted at Harry to get out of the way, comparing him to his father and saying he would have died just as arrogantly. In a split-second decision, Harry raised his wand and yelled "Expelliarmus!" At the exact same moment, Ron and Hermione also shouted the disarming charm. The combined force of the three spells created a blast that rattled the door on its hinges, lifted Snape off his feet, and slammed him into the wall. He slid to the floor, knocked out, with a trickle of blood oozing from under his hair. His wand soared in a high arc and landed on the bed next to Crookshanks.

Consequences and Aftermath

The immediate consequence was that Black and Lupin were freed from Snape's threat. Black, who had been about to attack Snape himself, looked at Harry and said, "You shouldn't have done that... You should have left him to me." Harry avoided his eyes, unsure even then if he had done the right thing. Hermione, staring at the unconscious Snape, immediately recognized the gravity of their action, whimpering, "We attacked a teacher... We attacked a teacher... Oh, we're going to be in so much trouble." Lupin, now untied by Black, thanked Harry. This act of defiance allowed the subsequent revelation of Pettigrew's true identity to proceed without interruption. Later, Snape would claim to Cornelius Fudge that the three students had been "Confunded" by Black, a story that Fudge, eager to close the case, readily accepted. Snape's humiliation at the hands of three students deepened his grudge, and he later retaliated by revealing Lupin's lycanthropy to the entire school, forcing Lupin's resignation. The event also cemented the bond between Harry, Ron, and Hermione, who had acted together in a moment of high-stakes moral choice, choosing to trust their instincts over the authority of a teacher.