Disclaimer: I don't profit from fanfiction.
A/N: I wrote the first part after HBP came out, but I left it unfinished until now, almost a year after DH.
"So," Voldemort said softly, as one by one, Greyback, Snape, and the others crawled towards him and kissed the hem of his robes. "I judge by the abject manner of your return that something in the plan has gone awry." He paused. "Dumbledore lives?"
The others kept their silence fearfully. All eyes were on Draco as he lowered himself to his knees to approach Voldemort. Voldemort stopped him with his upheld hand.
"Draco, Draco," he murmured, his voice a parody of solicitude and sympathy. The others had stepped back, leaving Draco to bear the full weight of Voldemort's attention. "You haven't the air of a killer. Your hand has never yet conducted the power of an Unforgivable."
He raised his head and sniffed the air horribly. "But somebody reeks of death. Someone has cast Avada Kedavra tonight."
"My Lord," Snape said, advancing a little, head bowed. "I killed Dumbledore."
"That wasn't the plan," Voldemort said, raising his eyebrow. "Look at me, both of you."
They raised their eyes to him. He asked them simple questions, all the while rifling through their emotions and thoughts with Legilimency to see if the contents of their minds matched those of their answers. Snape did his utmost not to flinch while carefully stowing away potentially treacherous thoughts into secret mental compartments and smoothing rugs over the trapdoors with Occlumency. His shoulders quivered imperceptibly with fear of what would happen if Voldemort detected his use of Occlumency. He feared also that Draco's ability was not advanced enough to either deter the Dark Lord or disguise his use of Occlumency against the Dark Lord's discernment.
"You may go," Voldemort said at last. "I expect Narcissa will want to thank you, Severus." A smile played about Voldemort's lips.
"My Lord," Snape and Draco murmured, bowing on their way out. Once outside, Snape seized Draco roughly and Apparated in front of his home in Spinner's End.
"What the—what is this place?" Draco demanded as Snape opened the door with a flick of his wand. "Why the hell have you brought me here?"
"In!" ordered Snape, using the authoritative tone that Draco had long been conditioned to obey. "I want to have a few words with you before I take you back to your mother."
"Like what?" snapped Draco, striding into Snape's lit living room with ill grace. After a quick glance at his surroundings, his nose wrinkled in distaste. "Surely this isn't where you—?"
"Sit," said Snape forcefully. By force of habit, Draco had actually taken a step towards the threadbare sofa before stopping himself.
Glaring at his former professor, he sneered, "What are you going to say? 'I told you so'? So you did get to steal my glory, you did get to stay in his favor, and the old man's, too, up till the very end—so what?"
He noticed Snape looked slightly ill; his face seemed painfully drawn. He had heard Snape raging indistinctly at Potter during their flight and wondered whether that had anything to do with it. Conversely, Snape was scrutinizing Draco with equal interest.
Even in the flickering, yellow candlelight, he could see Draco's extraordinary pallor; and even in the dark room where Voldemort had received them, Snape had noticed Draco's voice was about an octave higher than usual, and as tremulous as a reed in the wind. He therefore let Draco's petty words slide off the side of his face like so many melting snowflakes. He had to penetrate the heart of the matter, quickly and in a manner transparent to Draco.
"Did you employ Occlumency against the Dark Lord?" asked Snape brusquely.
"I already told you, I don't have anything to hide from him, I just don't think it's any of your business!"
"Stop this," Snape said coldly. "He certainly used Legilimency on you while we were being questioned; I felt him in my mind as well. The Dark Lord's last words to us before we left ought to have alarmed you: If he knows that I made the Unbreakable Vow to your mother, it is to no one's advantage—neither yours nor mine nor your parents, do you understand?"
"What do you mean?" Draco retorted, trying but failing to sneer as though Snape's words meant nothing to him. "Just because you have a soft spot for my mother or something—,"
"It would be dangerous for your mother," Snape hissed. "Your aunt might have told you! By coming here without the Dark Lord's knowledge, and asking for my help, Narcissa put her family ties above loyalty to him."
Draco recoiled as if he had been slapped. Though he did not show it, Snape viewed this approvingly, for it proved that Draco was at least quick enough to grasp the ramifications of his mother's impetuous act.
"Why did she do it?" For the first time, Draco did not try to disguise his fear.
Snape made an exasperated sound in the back of his throat. "You haven't yet figured out that throughout this entire matter, the Dark Lord's wishes have been largely disregarded. However foolish it seems in retrospect, another's best interests were given priority over the Dark Lord's."
Draco sank onto the sofa and lowered his head.
"Accio wine!" Snape uncorked the bottle that soared into his hand, took a swig, and offered it to the boy. Draco made a small moue of distaste (of course, at home he drank out of the finest crystal), but he took it and chugged nearly half the bottle.
When he handed the bottle back to Snape, some color had returned to his face and his eyes were bright.
"Why did you make the Unbreakable Vow?"
"Because I had every intention of keeping it."
Snape scowled, but not without some hidden satisfaction, at Draco's stunned silence. The boy understood a lot more than he had an hour ago on the tower. It was enough, he decided.
"Time to go," he said for the second time that night, standing up and leading the way out. "Narcissa must be half mad with anxiety by now," he muttered, mostly to himself.
Behind Snape, Draco averted his gaze from the man's back, and said quietly, with a year's worth of shamed apology in his voice, "Thank you, sir."
Snape elevated his eyebrows in surprise, and slight exasperation. "Let's get on with it. If you were to thank me properly for all I've done for you this year, we'd be here the whole night."
Twenty years later, as Draco stood over Snape's grave, he raised a glass of the finest elf-made wine that the Malfoy cellars boasted.
"Before Scorpius was born, I wanted to name him after you. Scorpius Severus rolls off the tongue, don't you think? Father didn't think it was entirely appropriate, but Mother understood. But then I found out that Potter had beaten me to it and named his brat Albus Severus, so fuck it, I let Astoria name him after someone on her side of the family."
Draco grimaced. "Kind of wish I hadn't, now. Hyperion is a bit pretentious, even for a Malfoy.
"Anyway, Scorpius wouldn't be here—shit, I wouldn't be here—if not for you. Which means that if not for you, I might not have lived to see my hair fall out, and you're probably having a great laugh at my receding hairline right now wherever you are, you bloody wanker. You were one hell of a professor, and an even better spy. Thanks for everything."
Draco drained his glass, and picked up another one that he had set atop Snape's tombstone.
"One last thing: I've come here every anniversary of your death for the past twenty years, and I still haven't thanked you properly for everything you did for me that year. So you were wrong about one thing.
"I mean, the whole night? I'm going to be here thanking you for the rest of my life. Cheers, Snape."
Draco poured the priceless, several hundred-year-old contents of the glass onto the ground. His father would have screamed bloody murder, but Draco knew that it still wasn't enough. As he watched the fine wine soak into the ground, he wondered what Potter's annual ritual consisted of. A fresh set of footsteps that didn't belong to Draco led towards Snape's grave, and away all the way past the gates, where the anti-Apparition wards stopped.
Just as Potter had been first to claim Snape's name for his son, he also beat Draco here to pay his respects every year.
Turning to go, Draco said, "If I ever do get here before Potter does, I'll leave some of the wine for him. That'll show him how we honor one of our own."
He imagined Snape's smirk at that, and the memory carried him all the way past the gates, where he turned on his heel and Apparated, leaving Snape's grave silent and lonely once more—at least for another year.