Prologue:

"Ner ner ner nerner, can't catch me-ee!" caroled Sirius as he ran down the second-floor hall of 12 Grimmauld Place. He didn't quite know why he bothered, as Regulus certainly couldn't catch him with his legs stuck together, but making a lot of noise when there were dozens of relatives in the house was satisfying. There were certainly enough of them at the moment, crowded into the house to celebrate the coming-of-age of his cousin Bellatrix. Such occasions always brought swarms of ancient Blacks with dusty cloaks and dustier minds out of the woodwork, mouldy old fogeys and terrifying matrons from every corner of the world. If it was possible, Sirius disliked them even more than he did the permanent inhabitants of Number Twelve, Grimmauld Place

Unfortunately, some of those mouldy old fogeys weren't totally deaf. "Sirius Orion Black! Stop that noise AT ONCE, do you hear? There are GUESTS in the house. Come here!" That was his grandfather. Not so bad as upsetting Mother – he tended to forget quickly – but teasing Regulus wasn't really worth the trouble.

Sirius stopped the noise but, instead of going downstairs to be punished, raced into the Green Drawing Room and – stopped dead. An immensely old man with a huge nose and hardly any hair was sitting in an armchair by the fireplace, with a half-full decanter of something amber-coloured on a side-table and a battered, leather-bound book in his hands. Sirius thought he was asleep, but a gruff muttering from the armchair proved him wrong,

"Dammit, hasn't he heard of a Drying Charm? He married old Morrison's niece, surely he knew. She couldn't possibly have not told him for seventy years, however dense the man was. That's good, though. That's dashed good. A hand-rail round Hyde Park, indeed. Young Sirius might give him a run for his money, there, if half what that good-for-nothing-"

Shocked to hear his own name, Sirius spoke up, "Yes, sir?"

"What's that? Who? Oh, hello there. You'd be Selina's boy, would you?"

Sirius didn't have the foggiest idea who Selina was, but was reasonably sure he wasn't 'her boy', "No, sir. I'm Sirius. You… were talking about me." Sirius found a bit more courage, "And anyway, who are you? All the other old- er, guests are in the dining-room."

The old man chuckled throatily, "You're Sirius? I can see what dear old Cassandra means. You'd be my, let's think now, great-nephew? I'm Alphard, youngster. Pleased to meet you." The old man held out a hand, which Sirius shook gingerly.

"Er, and you, Uncle Alphard." Sirius had never heard of an Uncle Alphard, and hope sparked within him that this wasn't another old git who'd lecture him on purity and propriety, shake his head over a Gryffindor in the family and tell him off for causing a racket. The next words almost dashed this hope.

"Come to look at the family tapestry, have you? Get a look at your glorious forebears. Follow the untainted line of descent on both sides from John of Gaunt himself?" His face might have screwed up slightly, but under the wrinkles it was difficult to tell.

Sirius had forgotten this was the room with the family tree, which he normally tried hard to avoid, "Are you – no, Uncle Alphard. Not today." No sense in upsetting the old geezer just yet, thought Sirius. He's still better company than Mother's friends downstairs, or Kreacher, or…

"You should, boy. There's a wealth of stories between those lines."

Yeah yeah, I know, said Sirius under his breath, proud Wizarding tradition, Slytherin since the Founders' day, heard it all before. But the old man continued,

"Look at these dates. Go on boy, closer. The tapestry doesn't bite – at least, it never used to. Can't tell what Walburga's done to the old place over the years." Obediently, Sirius knelt to look at the huge family tree, feigning concentration on the gold lettering where a gnarled hand reached out to touch a particular line, "Notice anything strange there?"

"Well, only that my granddad was… thirteen? That can't be right. He was the same age…" Sirius trailed off, bewildered. His grandfather was young, but surely he couldn't have been that young. Maybe it was a mistake.

"As you are now, yes. Or rather, no. You see, the family" – definitely a sneer there – "isn't quite as pure and righteous as your mother would like to think. Irma, lovely, innocent Irma. No sense, that gel. None at all. Took after her grandfather." The old geezer seemed to have forgotten his point, but abruptly came back to it, "Be that as it may, you don't really think a boy in his third year of school fathered Walburga, do you?" From his tone, it was obvious that the idea was absurd.

Sirius couldn't quite see it; Marcus Davies was only a fourth-year and he'd, well, Sirius wasn't quite sure what, but he'd done quite a lot, "Why not? I would – maybe not with anyone related to Crabbe." He was more than a bit unnerved by this old man and his idea of a fun afternoon, but did his best to project an air of worldly braggadocio. The idea of Crabbe – a large and vicious Slytherin sixth-year – was definitely unsettling in this context.

"Heh, I don't doubt it boy, though Irma might have been more to your taste than her nephew, but poor young Cygnus wouldn't have known what to do with a woman if she'd stripped naked and dragged him into the bushes." Sirius liked this idea much more than tales of perverted ancestors and drifted off into a pleasant daydream about that sixth-year in Ravenclaw, then came back to earth with a bump.

"Cygnus Black wasn't your grandfather at all, Sirius. Any fool should have guessed that, though they all pretend not to know. No, Walburga's father was – well, I'll have to start at the beginning. It was in the summer of '24, I think, and Irma Crabbe had, let me see, just left Hogwarts, that's right. Stop me if I'm boring you."

For once, boredom was the last thing on Sirius' mind. He wanted to know who his grandfather was, and why a thirteen-year-old boy had had to get married, and…

A/N: Sorry the prologue's a bit short. This fic was inspired by a discussion on the Canon Quick-Check thread in the Sugar Quill forums (sugarquill dot net), in which the dates on the Black Family Tree were dissected and found impossible. Maybe, I suggested, this was done deliberately, to hide the 'undesirables' of the family history. Here's the story one of those undesirables, whom you may recognise. Before the Holy Grail, before the Ark of the Covenant, before monkey-brains and Short Round, were the Sword of Caractacus and a young Irma Crabbe. Enjoy!

A/N on the A/N: This is therefore at least a 3-way crossover, but no knowledge at all of the other two canons is required. I can't tell you what they are, as that would give away too much of the plot. One is very minor and you'll have to pay attention to notice it at all.