Disclaimer: Harry Potter © J. K. Rowling
In the middle of the Battle of Hogwarts, Severus Snape came to the Boathouse in order to have a talk with Lord Voldemort who summoned him a few moments earlier. While the Dark Lord was walking towards him, he gave him a compliment, "You have performed extraordinary magic with this wand, my Lord, in the last few hours alone."
"No! No! I am extraordinary," he boasted. "But the wand… resists me."
Snape stated, "There is no wand more powerful. Ollivander himself has said it." He tried to convince him, "Tonight, when the boy comes, it will not fail you, I'm sure of it. It answers to you… and you only."
However, Voldemort still questioned him. "Does it?"
"My Lord?"
Voldemort walked in circle around him, wondering if the Elder Wand truly answered him. In his opinion, Professor Snape was supposed to know who the real master of the wand was.
Snape lied to him, "With you… of course, my Lord."
Voldemort replied, "The Elder Wand cannot serve me properly because… I am not its true master. The Elder Wand belongs to the wizard who killed its last owner." He spoke again, walking closer to him, "You killed Dumbledore, Severus."
Unexpectedly, Snape was brave enough to interrupt when Voldemort was still speaking. "But Dumbledore won the Elder Wand without murdering Gellert Grindelwald. Instead, you're the one who killed Grindelwald with the Killing Curse. Is that correct, my Lord?"
"Oh shi-" Voldemort whispered to himself. "Wait! How do you know that, Severus?" he asked before Snape managed to tell him that there was someone who successfully disarmed Dumbledore before he killed the former headmaster.
The Half-Blood Prince smirked at him. "Read the book again, Voldy. Have you forgotten what's written regarding Grindelwald?"
And… CUT! Voldemort got a little embarrassed, realizing that he was tricked. Still, he enjoyed laughing along with Snape.