Severus Snape had made a poor decision, once in his youth.

Oh, it wasn't that he had decided to join the Death Eaters, or even that he chose to turn spy on them later. It wasn't the time he agreed to attend a Yule banquet at Hogwarts as a teacher, where Dumbledore had put a magenta cap upon Snape's head and fixed it there with a Sticking Charm, which meant Snape had never attended another Yule banquet since. No, it was that one time he had willingly slept with Bellatrix Black when he was 19 years old and newly-initiated into the Death Eaters.

It had been a one-time occurrence, since Bellatrix, at 28, had already begun showing signs of her imminent insanity, and Snape had wanted to get as far away from that disaster as possible. Not long after their liaison, Bellatrix had taken to acting very oddly around him, sometimes latching onto his arm with talons digging into his flesh, or ignoring him completely in favour of courting Rodolphus Lestrange, who seemed overwhelmed by the attentions of an older woman. A few months later, she disappeared for several months, but the Dark Lord had seemed mostly mollified by whatever excuse she must have given him.

Rumours ran rampant.

Bellatrix had fallen victim to a curse that required long recovery. She had run off on mysterious reconnaissance work for the Dark Lord. She was having Lestrange's baby in secret.

Then, six months later, she returned. Bellatrix outright ignored any questions as to her whereabouts, even from her sister. No longer did she cling to Snape's arm and blink her wide brown eyes up at him, but secured herself firmly to Rodolphus, who seemed resigned to his position in life. They were married within three weeks of her return.

Another year passed, and the Dark Lord fell. The Lestranges all went to Azkaban, and Snape found himself roped into teaching Potions at Hogwarts. His life fell into a frustrating pattern of teaching, marking and supervising detentions. All the while, the Dark Mark lay faintly in his skin, a reminder that his life as a Death Eater could not possibly be over.

Years passed. Harry Potter appeared in his classroom, infuriatingly bright-eyed. If only that had been the extent of Snape's problems that year.

In June, Potter had somehow finagled his way past that monstrous three-headed dog and the rest of the enchantments protecting the Philosopher's Stone, nearly getting himself killed in the process of facing down the Dark Lord's soul. The next year, he wiggled his way into the Chamber of Secrets and slayed a basilisk, of all things. Snape was still upset about the loss of an endless source of basilisk ingredients, which could have been sold for a minor fortune, if anyone had just asked him. Then, two years later, the Dark Lord had regained a body and Snape dreaded his future once more.

He bowed, he groveled, he brewed, he was hit by the Cruciatus more than once. And then the Dark Lord announced that there would be a mass break-out from Azkaban, so that his most loyal followers would be released to him. And sure enough, Bellatrix was back, crazier than ever, with her husband at her side.

Snape paid little attention to her eccentricities; they would make his mind spin and he honestly wanted nothing to do with her. But Rodolphus seemed to think that Snape was willing to lend an open eat to all his problems.

"She disappears, you know," Rodolphus said quietly as they sat in Malfoy's green wingback chairs, leaning over a chessboard. "For days at a time. Always a bit... happier, when she returns. I wonder, sometimes, if she's having an affair. Not that I mind, mind you. I'd just like to know. I hate being ignorant."

"Perhaps she has a book club to attend," Snape suggested as he moved his knight, removing the second of Lestrange's bishops from the board.

"In Azkaban, she kept screaming this name, you know. At least, I think it was a name. Not a man's name, mind you. But a name, nonetheless." Rodolphus trailed off thoughtfully.

"Are you going to tell me this name or aren't you?" Snape asked after a long pause.

"Hydra." Rodolphus bumped a pawn a space forward.

"The sea monster?"

"I suppose so. I just don't understand why she would be so obsessed with it."

Snape took a moment to remove Rodolphus' pawn from the board. "Hydra," he said thoughtfully. "Just the name?"

"It's all she said. Sometimes called out for her mother, too. Asked her to care for something."

Well, that was interesting. The pieces on the board rattled around for another few minutes before Snape slid his queen into place. "Checkmate."

Rodolphus knocked his king over. "Never stand much of a chance against you, Severus." He didn't seem too upset about it. "Listen, you're a handy one for listening at keyholes..."

"I hardly listen at keyholes, Lestrange."

"I was simply wondering..."

Snape pursed his lips briefly. "You want me to keep an eye on your wife." It was not a question.

Rodolphus nodded once, quickly.

"Well," Snape said, leaning back into his chair. "I might be able to rustle up an interesting fact or two for you."