This is based in my "Snape's Memories timeline. You'll need to read that story for this to make much sense.
It was uncommonly cold, this Christmas holiday, at Hogwarts.
No Christmas trees graced the Great Hall this year, although there was one in the staff room and the hospital wing. The staff eschewed the usual merriment this year, opting for more private gatherings.
The Carrows were spending this Christmas Eve carousing with the Dark Lord's inner circle. Severus had been to that meeting and then made his excuses. Fortunately, he was known for his dislike of relevry, so it wasn't taken amiss.
Then too, Amicus had been helpful by informing the Dark Lord of Severus' activities. He had giggled through a description of Severus' supposed molestation of the Weasley girl that the Dark Lord found most entertaining.
The Dark Lord had smirked (the sight was enough to make one's blood run cold), and said, "You see, Severus, it is as I said. Better women, for the taking. Will you keep her, do you think?"
Severus had inclined his head, manufactured thoughts running through his mind of what had supposedly taken place with Miss Weasley that night. The Dark Lord had practically cackled with delight at the thought of the girl's debasement and deflowering.
By the time Severus had gotten away from the Death Eater's celebration he felt like he needed a shower.
More than usual.
Fortunately, Miss Weasley seemed to understand that the only thing keeping Amicus from following up on his own threat was Severus' supposed interest in her. She had never contradicted any of the dark suppositions of her compatriots.
He occasionally caught her staring at him in the Great Hall.
She was gone home now, with the rest of the students. None of the students had stayed. Not one. This was fairly unusual, but these were unusual times.
Severus paced through the front entrance, closing and locking the doors with a flick of his wand.
He wished for a moment that his path would have led him to the dungeons and his old quarters. Instead, he wearily climbed the stairs to the headmaster's office.
Passing the hospital wing, he heard the low voices of Filius and Minerva, conversing furtively with Poppy. In other years, he would have joined them. In other years, Dumbledore would have been there, inviting him in.
Minerva opened the door to the hospital wing, just in time to meet Severus as he came past. She spoke no word of greeting, but her eyes blazed with hatred at the sight of him. She turned quickly, as if she couldn't stand to look at him, hurrying down towards her own office.
Severus' stride never varied. He felt the eyes of both Filius and Poppy on his back. He looked neither right nor left, though his heart broke a little more.
He finally made it back to the safety of his room, where he locked his door behind himself. He threw himself into the chair behind his desk. With relief, he summoned a stiff drink to his hand.
This one night, the Dark Lord would not call him. Not because of the wretched holiday, but because the mad bastard was deep into some scheme to catch the bloody Boy. The Dark Lord was meeting with his spies and informants tonight.
It would not be wise to get as drunk as he'd like to. Severus sat wondering if he cared to be wise anymore.
A faint tapping alerted him to someone at the door before he could really make up his mind.
He flicked his wand to open the door, "Come." he called, not bothering to get up.
It was Poppy. She peered around the room, perhaps checking to see he was alone. She came in through the door, only coming in far enough to close the door behind her.
"To what do I owe this surprise?" asked Severus coldly, "Is there some new crisis you need me to sort out?"
"No, thank you, Severus." She said, softly, "I only came to wish you happy Christmas. "
She had worked at the school since before Severus had become a student, and had always been rather kind to Severus. This year, however, his only interactions with her had been characterized by the hatred and thinly veiled contempt the other teachers held for him.
He felt strangely wrong footed by this well wishing.
"Is that all?" he asked, still coldly.
Curiously, she smiled at him, "I know how well warded your quarters are, Severus." She was holding her hands behind her back, as if she were hiding something.
"If you mean to murder me, I should remind you that I can quite likely best you in a duel. It would be a shame to kill you. The students still need your skills." Severus replied, poisonously. He hoped sincerely it did not come to wands between them, on Christmas Eve, no less.
She drew her hands back around in front of her, revealing that she held a small silver box, "Severus." she said, quietly, "Please. It's Christmas and I thought you..." she faltered, "I wanted to give you this."
Severus blinked as she lay the small silver wrapped box on his desk, only now registering that Poppy had called him 'Severus' rather than 'Headmaster' as she had been doing all term.
He stared at the box, which was no bigger than a deck of cards, "A rather unimaginative way of getting rid of me, don't you think?" he sneered, "Set to blow up the minute I touch it?"
The witch looked Severus directly in the eyes, "I wouldn't want to do that." she said softly, "I can't imagine that anyone would be able to protect the children, with you gone."
Severus felt his pulse quickening, "I have no interest in protecting these brats." He hissed, "I do what the Dark Lord tells me to."
She nodded, her eyes shadowed, "Yes, I see that. I also see other things." She moved away from the desk, "You know, I doubt the Carrows would notice if the Evil Headmaster made it his habit to come by the hospital wing to take inventory and criticize the state of my potions cabinet. My office is as well warded as your own."
Severus stared at the woman.
"The other staff are leaving tomorrow to have Christmas dinner together in Hogsmeade. I told them I would be dining with a friend. He is having a terribly hard time with the War, you see." Poppy moved back towards the door, "If you want to find me, I'll be in my office at five o' clock."
Severus blinked again, "Surely you aren't inviting me to Christmas dinner?" he said slowly.
Poppy stopped with her hand on the door, "Yes, I am." Was all she said, and she opened the door and made her way down the stairs, leaving Severus alone with the silver box.
With a quick wand wave, Severus checked the box for Dark Magic and hexes. The box's magic was only of the healing kind, he discerned.
He ground his teeth together, wondering what Poppy was playing at. Was she trying to get herself killed? Even if she did suspect his double agent status, she had no call to be taking such risks.
He opened the box. A gleaming vial of potion lay inside, with a label tied around the neck.
Severus stared for a long moment at the cloudy silver potion, as it swirled in its bottle.
Heart's Ease was a powerful potion, with a deceptively innocuous name. Its use had been restricted by the Ministry of Magic for its addictive qualities. Muggle fairy stories that spoke of people being spirited off to the Land of the Youth were based on its effects. Severus himself had never made it, and certainly had never taken it.
St. Mungo's used it for cases of intractable depression and magical shock. In the right circumstances, it had been known to work miracles. Severus wondered how Poppy had procured it.
A small dose would render the taker insensible for fourteen or so hours and the taker's dreams would be wondrous; or so it was said. The dreams would be exactly what the taker would need, they would soothe whatever pain the taker needed to soothe.
Severus flicked his wand, locking the office door. He picked up the small bottle, and with a feeling of letting go of something, cracked the seal and tipped it down his throat.