A/N: This is a very angsty little piece so read at your own risk. Just a little one-shot plot bunny that wouldn't get out of my head. I should probably be working on the next chapter of Book of Days, so I'll get back to that now.

Not beta'ed, so all mistakes are mine.

The first time Hermione suspected that Severus was a Death Eater- current, not former- they had been together for just over a year. She knew, of course, that Severus was a spy for the Order of the Phoenix. The information he brought the Order was invaluable, and Hermione had always resented the fact that he received so little recognition for his actions.

But after discovering the Severus' latest correspondence to Lucius Malfoy, Hermione couldn't be so sure that Severus really was on the Order's side.

The letter, in and of itself, was innocent enough. Severus regularly corresponded with Malfoy as part of his cover. This letter, however, simply revealed far too many of the Order's secrets for comfort. Within the letter were all of the week's passwords for Hogwarts. Someone with access to this information would be able to get into virtually any room in the castle, including the Headmaster's office.

It could, however, simply be a plan that Severus and Dumbledore had devised, although Hermione failed to see what purpose it would serve. Still, she had to give Severus the benefit of the doubt; after all, he had sacrificed so much to the Order and she couldn't, or perhaps wouldn't, believe that he was a true Death Eater.

The second time Hermione suspected Severus of being less than loyal to the Order was when she walked into his sitting room while he was in the middle of a Floo call with Walden McNair.

"…mustn't let them become too suspicious. The plan…"

Severus hastily silenced the man when he became aware of Hermione's presence. "What are you doing here, Hermione?" he asked harshly, stepping casually in front of the fire to block McNair's profile.

"Sorry to interrupt," she hastily apologized, already beginning her retreat from the room. She gestured at the book in her hand, the one she had snatched from the table beside the door. "I needed this for my class and remembered I had left it here last night. I hope you don't mind?" The last was asked in a breathy voice, and Hermione widened her eyes innocently for effect.

Severus looked at her suspiciously, but when she flashed him a sexy grin, seemed to relax. "It's no wonder I forgot it after our little… encounter last night." She gave him smouldering look and relaxed when the corner of his mouth quirked.

"Indeed. Just don't come barging in again unannounced, Hermione. Common manners must be regarded, don't you agree?" His tone was mild, but it made her wary.

"Oh, absolutely. I'll see you tonight then." Then she fled, with as much casualness as she could muster.

When she was finally outside of his rooms, she leaned heavily against the cold stone wall and willed her frantic heart to slow. Her mind struggled with what she had heard.

"…mustn't let them become too suspicious. The plan…"

The words were, at the very least, disconcerting, and coupled with the letter she had found some few weeks before, very nearly damning for Severus.

But Hermione was nothing if not forgiving. She wouldn't condemn a man, especially not one that she loved, with such circumstantial proof.

So she resolved to learn more, because she was nothing if not a thorough researcher.

Firstly, she charmed all the quills in Severus' quarters to replicate the last things they had written onto another piece of parchment. Since Hermione was often in and out of his quarters during the day (although she had her own quarters in the castle, she practically lived with him), she had ample opportunity to gather her evidence. She had worried that he would discover the charm, but after a few weeks and dozens of copied letters with no mention from Severus, she felt more confident.

The information she had collected from the quills was disturbing. Every week, without fail, Severus sent a letter to Lucius Malfoy with the week's passwords. He was also leaking information from the Order. These were not trivial secrets like Dumbledore often had him satisfy the Dark Lord with, but serious matters, secrets the Order could not afford to be known.

Hermione did find it odd that he would send such important information to Malfoy via Owl Post, although she knew he only ever used his own owl, Mnemosyne, to send his mail. So when his next letter was due, Hermione cancelled her classes and hid herself in his office, shrouded in Harry Potter's borrowed invisibility cloak and waited to find out. As he wrote, Hermione held herself deathly still. Barely even breathing she watched him write his letter. When he was finished, he took his wand out and glanced around the room. Hermione's heart thudded; she was sure he must of heard her. Instead, he simply held up the letter and cast an encryption spell.

When he had finally left the quarters, Hermione threw off the cloak and collapsed, gasping for breath and trying to quell her nausea. Shakily, she stood and moved to the desk where she copied the letter from the quill.

Only when she was safely within her own rooms, did she begin to panic. For hours, Hermione cried and raged, angry at and devastated by the man she loved. Eventually, numbness crept over her and she slumped into her couch only to be roused by a flare of green from her fireplace.

"Hermione," she heard the familiar voice say. "Were you not coming to dinner tonight?"

Hermione tensed, but she eventually willed herself to relax before answering, "Of course, dear. I didn't realise it was so late," she lied. Snape's features were frightening in the green relief of the fire.

Curtly, he nodded and ended the call and Hermione collapsed back into the couch. How could she pretend to be comfortable around him knowing what he was doing? She knew he would expect her to come back to his quarters after dinner; it was what she did every night.

Hermione had returned to Hogwarts two years ago to become the new Defence Against the Dark Arts professor. Tired of being an Auror, she had welcomed the job offer and, by some stroke of luck, had broken the curse of the position by lasting for more than one year. She and Severus had danced around one another for months before finally becoming lovers. She thought she'd known everything about him. She couldn't believe how wrong she'd been.

Resolutely, she made her way to the Great Hall for dinner. She took her customary place next to Severus and ate the suddenly tasteless food. When dinner ended, she woodenly followed Severus to his rooms. When he pulled her to him, she did not resist his advances.

Later that night, she left his rooms. When she reached her quarters, she stripped and scrubbed her skin raw in a scorching bath.

The next morning, she took her evidence to Dumbledore.

"Preposterous!" the old man exclaimed after hearing Hermione's allegations. "I've known Severus since he was a first year and I assure you-"

"How can you ignore the evidence!" she yelled over him. He quieted, his blue eyes boring into hers viciously.

"I admit it's disturbing, but Severus knows what he's doing," Albus said quietly.

Hermione snorted, astonished by the headmaster's naivety. "Oh, yes. He knows exactly what he's doing," she said bitterly.

Suddenly, Dumbledore seemed unbearably weary. He sighed and slumped back into his chair. Hermione knew what he was feeling; it was the same shocked disbelief she had been wrestling with for days. "I know you don't want to believe this," she said softly, catching his gaze. "I don't either. You and I are probably the only people who truly care for Severus, but we can't deny this evidence. He's betrayed us, Albus."

Old beyond his years, Dumbledore looked at her with suspiciously bright eyes. "What do you propose I do, Hermione?"

Hermione was shocked by his plea, and it took her a moment to respond. "If I'm wrong," she didn't add that she hoped she was, "I don't want Severus to suffer for it. I have to know for sure I'm right before we…" She trailed off, leaving the rest unspoken between them.

Dumbledore nodded in agreement. "We must know for sure."

"I'll continue to spy on him. He… trusts me. I won't rest until I discover the truth." Her heart broke as the truth of what she was planning sunk in. She was plotting against the man she loved, and if she were successful it would mean his death.

She put her head in her hands and sobbed. Eventually, Dumbledore sat beside her and wrapped his frail arms around her. Together, they contemplated the man whose fate now rested in their hands.

Using her formidable skills as an Auror, Hermione began her investigation of Snape in earnest the next day. Resolutely, she slipped into undercover mode. It was easier to investigate Snape if she stepped outside of herself and into a role. Over the next few weeks, she gathered more damning letters. She also began following him as he made his rounds, utilizing Harry's cloak yet again.

And every night, she went willingly into his arms, desperately hoping he hadn't betrayed them.

And then, three weeks after going to Dumbledore, the final piece of damning evidence fell into place. She had been following Snape, hidden by the invisibility cloak, during his rounds. When he was finished, he didn't return to his quarters, but made his way outside. Cautiously, he crept silently around the perimeter of the castle before pausing in front of a seemingly blank area of the wall. When he waved his wand in front of it, Hermione saw that there was in fact a concealed doorway. This was probably the portal he used to return from Death Eater meetings.

Hermione crept cautiously closer to observe what he was doing. He was deeply entranced in the spell he was casting, and with shock, Hermione realised he was dismantling the wards around the door. For minutes, Hermione watched him struggle with the powerful wards, wards set, no doubt, by Dumbledore himself. Successful, he slumped in exhaustion.

Hermione didn't go to him that night. She was still sitting in front of the hidden door when dawn crept over the horizon. Chilled to the bone, dried tears streaking her face, she knew she had been right.

Severus Snape was a traitor.

The letter he sent to Malfoy had been short.

The wards are down. We are ready.

Sickened, she showed Dumbledore the Pensieve of the night and the letter she had copied upon returning to the castle that morning. The evidence was undeniable. Snape was guilty.

It ripped her apart.

Dumbledore's eyes had been hard when he called Severus to his office. Severus had arrived promptly, a questioning look in his eyes when he saw Hermione.

"What did you need, Headmaster?"

Dumbledore waved him into one of the chairs before acting. As soon as Severus was seated, Dumbledore brandished his wand and disarmed and bound him.

Hermione gasped at the twin looks of betrayal in both mens' eyes.

Her hands shook and she couldn't look at Severus as Dumbledore confronted her lover. At first Severus was angry at the accusations, but when the extent of the evidence became clear, became silent.

Arrogantly, he spat, "Your Gryffindor whore has done her homework, hasn't she?"

Dumbledore grew furious. "She did what she had to." His power crackled through the room, suffocating Hermione with its intensity. "Why did you do it?" he demanded.

Hermione could feel Severus' eyes boring into her, but she didn't meet his gaze. Eventually he answered, "I did what I had to."

Voldemort and his Death Eaters attacked the next morning, but the Order was ready. Harry Potter defeated the Dark Lord and the light triumphed. Hermione earned the Order of Merlin, First Class for her work in discovering Snape's treachery.

Severus Snape was found guilty of treason by the Wizengamot and sentenced to death. Hermione was there when he was executed. It was her penance for her betrayal.

A week after his death, Severus Snape's will was read. He had left everything to Hermione, not the least of which was a wrinkled bit of parchment.

Hermione,

I want you to know that I forgive you. You gave me more out of this life than I could have ever expected and for that I am grateful. I know why you had to betray me. It's no less than what I would have done in your place.

The Dark Lord planned on killing you when he discovered our relationship. To save you, I had to betray you.

I did what I had to.

Severus

The parchment was still in her hand when Dumbledore found her. Her self inflicted Killing Curse had been brutally efficient.

She was buried next to Snape in the Forbidden Forest. They shared a single headstone. It read simply: Severus and Hermione.