Severus Snape looked at the headmaster with barely concealed incredulity. "Absolutely not."
"Severus, be reasonable," Dumbledore protested. "Have a lemon drop."
"Reasonable? Reasonable?" Snape took a moment to calm himself, impatiently waving away the proffered sweet. It occurred to him that the headmaster might have finally slipped into his dotage, but the infernal twinkling in Dumbledore's eyes suggested otherwise. "I fail to see the reason, Headmaster."
Dumbledore continued to smile benignly at his Potions master. "You have done outstanding work for the Order, Severus. No one would deny that. And, frankly, you are too valuable a spy to waste. Voldemort is concentrating his efforts on the Muggle world, and therefore that is where we need you to be our eyes and ears - with your new partner, of course."
Snape refused to be mollified by the rather obvious attempts at flattery. "Yes, but..."
"She is exceptionally gifted, Severus," Dumbledore continued over Snape's interruption. "She knows the Muggle world far better than you. And although she comes from a line of rather dark wizards, her loyalty to the Order is without question."
In Snape's defense, he was well aware that trying to make Albus Dumbledore see reason in instances such as this was nothing more than an exercise in frustration. The diabolical old man would inevitably have his way; nonetheless, Snape felt compelled to lodge a vehement protest. "My memories of her time here as a student are painfully vivid, Headmaster. 'Exceptionally gifted' is not how I would describe her."
Dumbledore sighed. "I know this is not easy for you, but we all need to make sacrifices above and beyond what we have already given. It is essential that we keep a close watch on the Muggles - and in order to do that, you need a partner."
Snape's hands slipped from his temples to grasp the edge of the desk, his knuckles whitening. "Yes... but Tonks?"
Note: This first chapter was written as a stand-alone short and a bit of a protest piece towards all-powerful Mary Sues that swoop in, have a spat or two with Snape and... well, you know the rest.
The rest of the story was inspired by it and *cough* well, a popular HP fanfiction gizmo.