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Battles of Severus and HermionePrologue
Four months after Dumbledore's demise on the Astronomy Tower and well before the final battle between the Light and Dark Wizarding world, Hermione Granger figured out that ex-Professor Severus Snape was still on their side. She had rerun all the available information through her logical processes and come to the conclusion that he could have only acted upon the direct command of the Headmaster and not the Dark Lord. She came to this conclusion for numerous reasons, chiefly because Snape had not carried Harry to the Dark Lord that fateful night. Neither had he done harm to any other faculty member nor to any of the students. Only Dumbledore fell at his hand. Given the grave condition of the Headmaster after the destruction of the ring horcrux and the effects of that last night's sojourn after the locket horcrux, perhaps it was merciful that he died instantly. McGonagall and Harry both were well aware of the extreme discomfort of the injury suffered at the ring's destruction. Harry could only surmise that the lake water was not helping his fragile condition. Even then, Harry still hated Snape with an unreasonable passion. It was much like Snape's apparent hatred of Harry. Thus Hermione knew that she had to be the bridge between these two powerful wizards if the Wizarding world was to defeat Voldemort and move forward. Neither man could be sacrificed.
With McGonagall's permission, Hermione sought out Snape. Two months into her search, she discovered a means of contacting him that did not involve owls or the floo network. Neither was Voldemort likely to discover the reconnection. She had found a way of charming Snape's remaining personal possessions into port keys. The ministry had confiscated most of his dark arts books and dark potions manuals.They left behind things they thought had no value – most of his clothes, except his Death Eater robes and mask, and his other personal articles as well as most of his potion ingredients. Hermione took a great chance when she first used the port key to find him. She had a hunch that he was not likely to be at a Death Eater revel or meeting at noon, thus she found herself in his presence. Her sudden appearance stunned Snape. Once he got over the initial surprise of finding his student standing in the middle of his bedroom/study at Spinner's End, he was able to begin setting up less chancy meetings with her. Wormtail still resided with Snape, even though Snape had carried out Draco's task. Voldemort was not pleased to discover Snape had failed to bring Potter along. He had repeatedly administered the crucio upon Snape. As a result, Snape was still walking with a tiny bit of a limp, noticeable to Hermione but not to others. At their surreptitious meetings, Snape passed along useful information about where horcruxes might be as well as major attacks planned in advance. Hermione relayed the information to Harry and to McGonagall. Harry and Tonks went after horcruxes while McGonagall let the ministry know of potential targets of Voldemort's wrath. Casualties mounted up on both sides.
After Harry destroyed the second horcrux, he began to suspect where the information was coming from. In a lengthy argument with Hermione, she finally disclosed her source. She was afraid that in the end, Harry might kill Snape for malice's sake. She did not want that on Harry's conscience. It would be more than enough to kill Voldemort and any other Death Eaters who got in the middle of their final battle. Besides, Snape was proving to be reliable source. Even though, he was still caustic and brusque, Hermione found some redeeming qualities in the man and told him so. Snape was as stunned by her revelation as he had been by her first appearance. No one had ever found anything of worth in him, save the Headmaster. Over the intervening months, he found it more and more difficult to tear into Hermione. He actually began to appreciate her great abilities and clever but elegant solutions to problems, outside his classroom. He never had really enjoyed teaching children. They made him uneasy. He preferred working alone or in concert with someone with the same strengths, as he possessed himself. He had a low tolerance for those less gifted than himself. When Wormtail was not around, he would invite Hermione to join him in his laboratory at Spinner's End. At those times, he found her company a pleasant diversion from the war without and the war within.
For her part, Hermione would bring him potion ingredients and then take the completed potions back to Madam Pomfrey. She found this a surprisingly tolerable arrangement. He was mentally stimulating when he was not being nasty. His nastiness diminished over time working with her, seeing her innovate alongside him. They found a rhythm to the work. Hermione began to appreciate Snape as a person and stopped seeing her former snarky potions professor when she visited. They had achieved as sense of friendship and collegiality over the months.