Disclaimer: I own nothing except my overheated imagination.
The Task
"Severus," said Dumbledore, turning to Snape, "you know what I must ask you to do. If you are ready…if you are prepared…"
"I am," said Snape. He looked slightly paler than usual, and his cold, black eyes glittered strangely.
"Then, good luck," said Dumbledore, and he watched, with a trace of apprehension on his face, as Snape swept wordlessly after Sirius.
"Curse that miserable dog Black!" growled Snape as he swept through the corridors, ignoring the startled students who scattered before him. "And that wretched bloody werewolf!" he roared, bursting into his chambers and slamming the door behind him.
"Cosseted, beloved, treated like pets!" he spat out as he rummaged through the drawer of his desk, "Black should be returned to Azkaban where he belongs, the cur! And Lupin…that wolf should be banished from society to live like the outcast he is. I should be the one who stays with Dumbledore, I should be his favoured one. Haven't I always stood by him?"
He paused for a moment, the self-righteous anger in his eyes dimming briefly, before he continued to search the drawer with yet more vigour.
"Yes, well, anyway…They get treated as trusted friends while I get sent to do Dumbledore's dirty work yet again. A-ha!" he exclaimed as his hand closed at last on the object he had been seeking. A small, black leather wallet, it was unremarkable in itself yet its contents would be unimaginable to most in the wizarding world. He slipped it into a pocket and left his quarters, his rage unabated as he stalked throught the castle and its grounds until he reached the gates. Slipping through them, he Apparated swiftly away, unaware of the eyes that watched him from a window, their usual twinkle dimmed in thought.
"Ah, Severus, it is a heavy burden I must place upon you. Yet none could carry it so well…" mused the headmaster as he turned away from the window and towards the expectant eyes that looked up at him.
Several miles away, Snape emerged from the dark, quiet alley, feeling naked and insecure without his usual concealing robes which now lay hidden behind a dustbin. It would not do to appear conspicuous here, he mused as he checked his pocket to reassure himself that the wallet was safe within, yet he wished he could complete the mission in his usual attire. Striding through the streets with a confident air that belied his anxiety, he soon reached the store that he sought, thankful that the hour was not yet so advanced that his presence there would be remarkable.
The transaction was soon completed and he returned to Hogwart's by his previous route, still burning with rage at the task he had been assigned.
"That flea-bitten mongrel and his miserable freak of a friend!" he thought as he snapped out the password that opened the way to Dumbledore's office.
What is his obsession with sweets, anyway?" he wondered in a mental aside as the staircase bore him upwards. Returning to his previous train of thought he muttered, "The old crowd indeed! Why should they be constantly treated with such favour while I get sent out on jobs like this? It's worse than that fiasco with the Philosopher's Stone and that damned three-headed dog. Fluffy! Hah!"
Arriving in the office, he ignored the headmaster's cheerful greeting as he strode across the room to dump his package on the desk before standing back with his arms folded forbiddingly across his chest.
"Severus, dear boy, how can I thank you?" said the old wizard, the twinkle fully restored to his eyes, "I know how hard this task was for you, yet what could be more important to our cause? After all, we don't want any of our comrades to die of hunger, do we?"
At these words, a shadow in the corner stirred and revealed itself to be Sirius Black in his animal form. He padded across the room before rapidly changing shape and eagerly seizing the package on the desk. Snape watched him silently, an habitual sneer twisting his lips as the pale, gaunt man pulled out the contents of the Safeway carrier bag.
"Severus!" he exclaimed in delight, "Meaty chunks in marrowbone jelly!"
And Snape backed away in disgust as the dog-man began to drool over the brightly-coloured tins of dog food. It would have been so much easier, he thought, to return to the Death Eaters as a spy for Dumbledore…