The Otter and the Snake
The first six Patronuses she cast never reached him at all. It was the seventh Patronus that first encountered his wards and disintegrated with barely a poof. It did, however, alert the former spy that someone had inextricably found him. He picked up at once and moved to another secure location. This time, it only took her three tries to find him again. Over and over, the cat chased the mouse around the isle until finally, with nowhere left to run, Severus Snape settled in the cave where Dumbledore had brought Harry the night he died.
It was not an easy existence, living so closely with the Inferi, but at least he felt safe. Augmenting the deceased Dark Lord's wards with his own, he felt assured that the otter-shaped Patronus would never find him there. He was correct. For three days.
Admittedly, he wasn't even sure why he was so afraid of a simple Patronus. It hadn't behaved in a particularly hostile manner the few times it had gotten close enough for him to see it. Perhaps it was the fear of what message it bore. He would never admit his apprehension might be attributed to whose Patronus it was.
So the day the silvery otter caught up with him again, Severus, after having been hounded all over England, finally decided to make his stand. Instead of letting his wards do the trick, he brought them down so he could personally divest of the intruder. A simple Deletrius spell was all that was needed.
Now a new game emerged, where the hunter became the hunted. No longer cowering in the cave, Severus emerged each morning prepared to defend his privacy. Eventually, however, the otter learned to dodge his spells and would agilely leap from rock to rock to try and escape demise. Not many could deny such playfulness, and cold-hearted as he was, not even Severus was immune to its charms. If he seemed to anticipate the arrival of the Patronus each day and perhaps not aim as carefully as he could, well, there was no one to witness the fact, now was there?
This sport continued for a while until one day, the otter arrived hours earlier than usual and caught the sleeping man unawares. He awoke to a familiar young woman's voice telling him that, "All is forgiven. Please come back." This time, there was no hesitation or inaccuracy as he blasted the Patronus into nonexistence. The rest of the day, even the Inferi chose to keep their distance from the darkly brooding wizard.
The next morning, when the otter returned, Severus was ready to blast it again before it could even deliver its message, but faltered at the last second. "All is forgiven. Please come back." Its purpose fulfilled, the otter looked up at him with expectancy. Severus tried staring him down, but the otter just blinked back in patient ignorance. The man sighed. Recognizing the other's capitulation, the otter leaped towards him and happily accepted being "scratched" behind the ears.
From then on, the otter would arrive each morning, deliver its six worded message—which Severus would duly ignore—and then play with the man until it dissipated into smoke, sometime during the afternoon. Severus had learned to conjure small, incorporeal fish which the otter would most willingly snatch from his fingertips.
It would be lying to say that Severus did not contemplate the offer that the otter repeated day after day. He had long ago dismissed the possibility that it could be a trap. She was a Gryffindor after all, not a Slytherin. What he didn't understand, was what possible reasoning she had for trying to lure him out. He had accepted the consequence of needing to vanish from the Wizarding world after he had killed Dumbledore. Had looked forward to it, actually. He did not doubt in his ability to disappear, and the added benefit of never having to see either his abhorrent students or suffer the wrath of the manic Dark Lord again was quite attractive.
But he had to admit, he was getting quite bored. As amusing as the otter was, it could not discuss the latest Potions techniques with him. Nor could it prepare or even appreciate a finely cooked meal. And as much as he hated to admit it, he did miss some of his compatriots. Minerva, whom he could always tease without fear of alienating; Hagrid, who always spoke to him with respect; Hermione, who…
Now when had he started thinking of her as Hermione and not Miss Granger? He thought back to the last time he had seen her—running with the Weasley girl to his chambers. Telling him about the Death Eaters. The look of complete faith in his ability to save them. Oh how he must have disappointed her that night. And yet…and yet here were her messages each morning for at least half a year now. Perhaps she had somehow found out about the former Headmaster's plan. Or maybe…she had somehow come to forgive him even without that knowledge.
Either way, something relaxed in his chest as he considered the possibility of returning to the world he had cast away. The next morning, when the otter returned, he listened to her voice one last time: "All is forgiven. Please come back." His mind made up, he lowered his hand to allow the otter to climb up to his shoulder.
"Come on, Otter. We're going back to your mistress."