It turned out to be easier than any of them had thought.
Once again, the poison for Beauxbatons provided cover. The work of the Dark Lord, as it turned out, is indistinguishable from the work to undermine the Dark Lord, at least in these early stages. They are currently poisoning a school of magical children, poised to take it over. If there were any unknown reinforcements, who better to ask than a former Hogwarts professor? McGonagall would have traveled there over the years, met with those professors, worked alongside them, read their research, corresponded-it made sense to interrogate her. Most static defenses of a castle like that would be based on Transfiguration anyway, and she was an expert in that. It is an easy sell to the guards. It is only a touch harder, bringing a mudblood along, but Severus could be intimidating when he wanted, and they know where he stood in the Dark Lord's favor.
-Not for long, when the poison failed, Lily reminds herself. They need a plan in case Severus fell further out of favor than originally anticipated. He had reassured her that there could be excuses made about deployment, who poisoned the river and why they were at fault, that he has already set a few brutes to take the fall, brutes no one would lose sleep over, but ultimately it is a chance they have already taken. There are so many ways, she realizes, that it all could go wrong. Horribly, gorily wrong. What punishment would there be for a traitor like Severus? What punishment could there be for her?
Of course her thoughts are dark as she walked down the hall to McGonagall's cell. They are surrounded by Dementors. Even the shadows look ravenous. She would have to practice the Patronus charm more when they got back home. She knows how to do it, of course, had already cast it, remembered from her days in the Order patchy though they were, but suspects when she tried to think of the memories she used to produce the charm before it would be a great soft blankness. Her only comfort, bizarrely, is the straight spine of Severus before her, following the guard Auror to the cell door that held Minerva McGonagall. And isn't that an odd thought, but it works. Anything to keep the despair from rising too high.
The keys are old, rusted, and the lock sounds half broken when the key is turned. But of course, they wouldn't need real security here. Even a perfunctory obstacle to escape would keep a captive trapped. The walls and locks are not the real prison.
"Don't stay longer than you have to. I'll be back in half an hour to take you out. Some people," the guard Auror inclines his head meaningfully at Lily as he speaks, "are more affected by the Dementors than others, if you catch my meaning, Master Snape."
He nods curtly. "I will expect you in a half-hour. Leave us."
The guard nods and strides away, leaving the half-ajar door for them to open.
Lily isn't sure what she expected, but Minerva McGonnagall looking hale and healthy and as if she is about to take ten points from her own house isn't it. She stands at the center of the room, her robes worse for wear but still herself. Lily can't imagine how she's done it. Minerva is rock steady and patient, hands clasped behind her back, as Severus casts the litany of spells to give them privacy. Lily's wand isn't on her-it was too risky to bring in case she were searched-so she waits patiently, eyes still downcast, maintaining the image.
Once he is done, he puts his wand away and stands, facing her. "You're looking well, Minerva."
"You as well, Severus," she replies icily. "I'll make sure I change that when I get out of here."
"Don't," Lily interjects, more pleading than she would have liked. "Don't, Professor, please."
Minerva recoils from Lily's words. "How could you do this, Severus? I remember how close you were in school, you were inseparable, and now you drag her around like a puppet-"
"I'm not a puppet," Lily says, louder. "And if anyone's dragging anyone, I'm dragging him."
They are both looking at her, now, shock evident on both their faces.
She steps forward, glances to Severus, and then gives a faint smile. "The fight against the Dark Lord isn't dead."
McGonagall's face doesn't change. If anything, it becomes more deeply troubled. Finally, she steps forward, bending toward her. "Lily-after what he's done-after what he's taken-"
Lily shakes her head, trying to shake the thought lose. "I know. I know. We don't have the time. I've made my peace with it for now. You just have to trust me. We are working together."
McGonagall glances at Severus again, unconvinced, and Severus' face is as much a mask as the Death Eater mask he wears. It's almost as if Minerva can see it there. She probably has seen it, Lily realizes. They both have, in battle, the masked man who cast unique and horrible curses, and wondered, is that him-is that the child I knew, once?
"There are bigger things than James and Harry, Professor. Bigger things than revenge. Like T.M. Riddle."
McGonagall's attention snaps back to Lily, and in the closeness of their faces the illusion of strength and health falls away as posture and shadow. McGonagall's face is sharp and hollowed, nervous, unready for this. She isn't protected, then. Just proud and fierce. And suddenly trusting. A calculus has occurred: these words, a key to a door they had only hoped existed.
"You know, then. The true identity of the Dark Lord."
Lily and Severus share a glance. Severus is the more adept liar, so he answers. "We have suspected."
"Tom Marvolo Riddle," McGonagall whispers, passing a hand across her brow. "Dumbledore was looking everywhere for more on him, before he died. He was convinced there was something in his past that would give us the power to defeat him. That he could not be simply killed outright." McGonagall sags. "He was right, wasn't he?"
They can't give her anything. They had agreed to that before they even came here: they can't know they won't interrogate her after they leave, or later, if things go wrong. "I'm sorry," Lily whispers. "We can't tell you."
"You don't have to tell me. After James died, did-do you know what happened to the cloak? You don't have to tell me where-"
"Yes," Lily answers, unsure of where this line of inquiry leads. She can feel Severus looking at her, now, from behind his carefully neutral face. "It's safe. They don't have it."
"Good. He has the wand, of course."
"The wand," Severus says, a question beneath his tone.
"The Elder Wand. One of the Hallows," McGonagall answers.
"The Deathly Hallows?" says Severus. "That's a children's tale."
"Not according to the Dark Lord," snaps Minerva, evidently not through with her fury at Severus. "Our sources-yes, boy, we had sources inside the Death Eaters that your friends don't know about-they knew he was obsessed with the search after he believed he defeated the prophecy. He took the wand from Dumbledore's body before it was cold. It was Grindlewald's before that, and a thousand others. And Dumbledore suspected that the Dark Lord already knew and perhaps even possessed the Ressurection Stone, leaving only the security of the cloak between him and possible immortality."
Of course. She doesn't remember the infant she read it to, but she remembers the story. Gifts given to three brothers by death itself, gifts that could protect the user from death. And the cloak, the invisibility cloak that didn't wear out like other cloaks, the cloak she used to sneak up to the boy's dorm in her seventh year, the cloak Sirius had returned, sat at this very moment in a damned mixing bowl under the sink of a home owned by a Death Eater, a home that was a gift from the Dark Lord himself.
Dumbledore knew what James had inherited and hadn't told them. Bastard.
But it isn't important now. What is important now was horcruxes, what they were, how to find them, how to destroy them. The Stone was something, but it could be a dead end-
"We don't have time for this," Lily says, over her shoulder to Severus.
"We think there is something else Dumbledore was investigating," Severus says, tentatively. "Was there anything else-"
"There were a thousand things," McGongall interrupts, rubbing at her temples. It's as if talking to them has begun to wear on her exponentially; all her years in this place heaping upon her. She looks to Lily. "You know how he was. Schemes within schemes. Even I didn't know everything. It was safer that way."
"You know enough. Think-was there any artifacts he was investigating, anything… powerful? Anything of historical or magical significance, or any items of significance to the Dark Lord himself? Perhaps even ones that were significant to Tom Riddle?"
McGonagall smiles a wan, sick, defeated smile. "Lily, there were a thousand things and more. I can't help you."
"Anything associated, maybe, with the locket of Salazar Slytherin?"
"Lily-" Severus moves to cut her off, but McGonagall tilts her head.
"No, I believe there was something. A house-elf." McGonagall's mouth works and she touches her temples again. "A house-elf that belonged to a woman-Hepzibah Smith. That's it. She used to run Borgin & Burke's, before even I was a student. She showed the young Tom Riddle two things in her shop, and he murdered her for it, and used a false memory charm to convince the house-elf she had done it. The locket of Slytherin and the cup of Helga Hufflepuff. It seemed important but it never came to anything." Her hands fall away, and exhaustion appears on her face. "That's all I know."
"It's more than enough," Lily says. "Severus-"
Severus isn't satisfied. "Do you know anything about Rowena Ravenclaw's possessions-her staff, her diadem? Or the sword of Gryffindor?"
But they can all hear the footfalls approaching, stopping before the door, rusty keys moving in a lock.
"No," says McGonagall quickly, "He couldn't have gotten the sword. It wouldn't go to him, it's not it's nature, and no one who followed him could get it. The staff is a myth, as far as we know. As for the diadem-"
Severus draws his wand, snapping it sharply through the air to shatter the charms protecting the room, then pointed it at McGonagall.
The old woman freezes. She door creaks open. Lily's eyes are already down.
There is a moment of frigid silence, and then Severus speaks, his voice cold and arch once more as he tucks his wand back into his robes.
"Too late," he says, "Next time, remember Dark Lord rewards those who help him." And with that vague lie in place as their only cover, he turns without looking at either of them to go.
Lily doesn't dare look at McGonagall again as they exit. It is too much to risk.
On their way back, the carriage is silent until they are almost all the way back. Finally, Lily speaks.
"What was her crime?"
Severus looks as if he's been woken from sleep. "Her crime?"
"What did McGonagall do to get put-there? In Azkaban?"
"Ah." He settles back further in his seat. "I believe the official charges were new ones. Encouraging magical theft by educating muggleborns, for example. Advocating for blood traitors. And so on." He shakes his head as if to clear it. "I wanted to protect her, but there was nothing that could be done."
Lily is surprised by this. And there's a kernel of hope in it, as well. "I wish we could get her out of there."
Severus' breath mists the window as he speaks. "It isn't possible."
"Isn't she an Animagus? Can't she get out on her own? As a cat? On our first day of class-"
He waves his hand to stop her, but he is still elsewhere, thinking, still focused on the impressionist landscape blur outside. "She was registered with the Ministry when it fell. The cell is specially warded against it. She can transform, but not pass the threshold. There are ways, I imagine, to fool the Dementors. But none of them involve leaving an empty cell."
Lily joins him in gazing out the window, the wind howling distant, ominous as his words. "At least she doesn't have to live through that place as a person. I can't imagine what that would do to a person."
He doesn't respond. He's still looking out the window, studying something inside his own head intently, brow drawn together and dark eyes closed.
But as the thestrals return and she reaches for the door, he places his hand on it. His words come out in a rush, as if he has been unsure if he should speak at all.
"Bellatrix Lestrange carries a cup with herself at all times. It's the only thing she'll drink from. It's small, made of gold, heavily enchanted-everyone assumes it was intended to heal her, to provide medicine with her wine, or at least to keep her under control." Severus swallows, as if he has wanted to hide this information but found himself unable. "I can't be sure, but-"
"Hufflepuff's cup," Lily whispers, both excited and horrified at how difficult it will be to take unnoticed. "She has it. In plain sight."