The air was bitterly cold and despite the many warming charms he had placed on himself Severus could hardly feel his fingers. He waited in the deathly quiet of the night, eyes fixed on the small glowing tent across the lake. He needed to wait for the correct moment. Too soon and his plan would be in vain, but any later and he risked discovery. Someone was bound to notice he was missing from his post soon enough.
The faint snap of a twig turned his attention to the other side of the lake, and Harry Potter emerged from the tent. Harry sat down heavily and lit a wand. Protective enchantments had clearly been placed around the tent (thanks no doubt to the Granger girl) but Severus had his ways of seeing through them. It was an old magic, which involved more complicated emotions than he cared to consider right now.
And so, before he could change his mind, Severus Snape raised his wand and launched his Doe Patronus into the frozen forest. The smiling face of Lily Evans came briefly into his head as the Doe made its way over to where Harry sat. Severus watched as the boy immediately got up and started following it across the woods. "Clearly he has learnt no more caution on his travels" Severus thought bitterly to himself, although he was pleased his plan was working.
He had never liked Harry Potter. The boy was undisciplined, argumentative and bore such a strong physical resemblance to his bully of a father that Severus sometimes found it extremely difficult to look at him. This could of course have been in part due to the fact that every time those bright green eyes caught his he was reminded of Lily and how he had failed her. Lily, her face crumpled with hurt that terrible day. She had never spoken to him again after that.
Shaking himself out of this reverie, Severus turned his attention back to the lake, and saw that the boy had picked his way over the ice. Severus watched as Harry pulled off his clothes and pointed his wand to crack the ice. Despite himself Severus was impressed. Potter had caught on much quicker than he had expected, and was showing his typical Gryffindor bravery by preparing to dive straight in. Reluctantly, Severus had to admit that this was more than bull-headed bravado. Potter was brave, there was no denying it.
And then he spotted the silvery glint of the Horcrux locket around Harry's neck. In that split second he contemplated revealing himself, yelling at the boy to take the locket off. Going into the lake with that evil thing on could not end well.
But he was too late. With another heavy crack of ice Harry had entered the water and dived down to retrieve the sword. Severus watched as the light of the Patronus died and the forest returned to darkness. Harry didn't surface, and nothing but a few bubbles broke the stillness of the lake. There was no sign of the desperate struggle happening underneath.
Severus' heart was in his mouth. He waited for what felt like hours but really could only have been moments before starting to unbutton his thick winter coat and make his careful way towards the lake. He cast a top up undetectable charm on himself and was about to leave his hiding place of a clump of trees when he heard heavy footsteps making their clumsy way over the ice.
It was the Weasley boy, who without even pausing to assess the situation dropped his bag and jumped straight into the hole Harry had left in the ice. He was clearly a strong swimmer because within seconds his head had broke the surface of the water, along with that of a gasping Harry Potter. Ron dragged his friend out onto the bank, trailing behind him, to Severus' immense relief, the glittering sword of Gryffindor.
Severus watched the reunion between the two friends with slight impatience. He needed to see the end of his own personal mission, needed to know that he had been successful in helping the boy destroy the Dark Lord. After a heated discussion Weasley raised the sword above his head and stabbed the locket with as much force as he could muster, smoke and fire emitting in a furious explosion. Severus did not stay to see what happened next. He simply whispered "good luck Potter" under his breath and silently disapperated back to Hogwarts to face his next task. Keeping the students alive for as long as possible.
The next time Severus Snape saw Harry Potter would be at the very end.
