"Severus." Dumbledore's voice followed him from the direction of the fireplace. "Perhaps you've forgotten that Lily's death was not because of me. It was because someone betrayed her and James's address to Voldemort."
Severus Snape's footsteps abruptly stopped. His back stiffened in the candlelight, like a black stone statue damaged from within and beginning to crack.
He slowly turned his head to look at Dumbledore, his eyes bloodshot. His fingers clenched beneath his black robes, his knuckles whitening, his joints creaking. He stood in silence for so long that McGonagall thought he would draw his wand and use some vicious curse she had never heard before on Dumbledore. But he did not.
He merely said in a low voice, "You'd better remember the promise you once made... You were the one who failed to protect her..."
Then he walked, step by step, from the sofa to the door. Each step was heavier and slower than the last, as though he were struggling through a swamp.
He walked out. The door closed behind him without slamming, settling smoothly into place. The latch clicking into the lock was as soft as a sigh.
McGonagall stood beside the desk with her head lowered, staring at her hands. Her fingers were spread wide, like claws that had slipped across ice, finally found purchase, and clung desperately to the frozen surface. Her breathing was heavy, so heavy it sounded as though she were breathing through her mouth.
"Albus, I—I didn't know he—" Her voice broke off.
Dumbledore reached out and placed a hand on her shoulder. It was not heavy, but it was steady. "I know. You didn't know. He never told you. He never told anyone." His hand withdrew from her shoulder. "But what he said was the truth."
McGonagall swayed again. This time,