Three Things:
1. I most certainly do not own Sleepy Hollow. Or The Legend of Sleepy Hollow. Or anything to do with Sleepy Hollow, really. On an unrelated note, I apologize for the 'S's. They were originally asterisks. Apparently, my computer has a problem with asterisks.
2. There's some Adaptational Villainy in here. Sorry, Katrina. (In The Legend of Sleepy Hollow, after Ichabod disappears, Katrina marries a guy named Brom. It is implied that Brom dressed up as the headless horseman to run Ichabod out of town. Apply that to the TV show, and you get… well, this.)
3. If "Katrina being a villain" ends up being cannon, somebody owes me a cookie.

SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS

On a cold night in October, Katrina's coven gets word of what the British are planning. They have a weapon. An ancient, horrible weapon that, if unleashed, could destroy the entire world. That same night, she sees him in her dreams.

She'd expected him to be terrifying.

Instead, he's just a man in a British uniform, with an iron mask on his face.

She wakes up with a start.

SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS

The dreams continue. Almost every night, she sees him. Death in a man's clothing.

One night, he speaks to her: Hello, Katrina.

She wakes, and lies very still for a long time, looking around the room. Nothing is out of the ordinary. She can't see any way someone could have come into the room and left without her noticing, and besides, why would anyone bother sneaking into her bedroom just to whisper her name and then leave? No, she decides, the horseman in her dreams was definitely speaking to her. She shivers.

"What's wrong?" Ichabod whispers, sleepily.

"Nothing. I thought I heard a noise."

"What sort of noise?" he's immediately on edge.

"Nothing," she whispers, forcing herself to keep her voice light. "It was probably just a mouse." Ichabod wraps his arms around her, and falls back to sleep. She lies awake for a long, long time.

SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS

She's having the dream again. She's dreaming, and she knows she's dreaming, but she still can't wake up.

What do you want, Katrina Crane? Power? I could make you powerful. The most powerful witch in the world, head of the most powerful coven. So powerful that the common people are afraid to persecute witches. Love? A husband braver, stronger, handsomer than sweet little bookish Ichabod Crane?

You could have everything.

You could have the world, Katrina.

If only you would reach out and take it.

SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS

The fighting is over, for the most part. Katrina walks across the battlefield, looking for survivors. And Ichabod. But mostly she is looking for a body, a certain body…

And there it is, just another corpse lying in the dirt, unremarkable except for the fact that it has no head.

And, she realizes, as she creeps closer to it for a better look, it's still moving. The finger of one hand twitches every so often, daring someone to notice it.

It speaks. Not out loud, and not in words, exactly, but she hears it nonetheless.

Hello, Katrina.

You want something from me, don't you? she wonders. She's not very surprised when he answers her.

Your husband is dying. If he dies, I die with him.

So I'll let the both of you die. Why does that matter? She feels a tiny pang of guilt, but she's not entirely sure what she feels guilty about.

He's your husband. Why would you let him die?

To rid the world of an evil such as yourself. Anyone else would do the same thing in my place.

Some would. Some wouldn't. Do you really want you husband to die?

No! No, of course I don't. But if you live…

If I live, I could help you. You know how powerful you could become with me on your side. The most powerful witch…

Head of the most powerful coven. They will be afraid to hunt witches because of me. The words sound sweet in her mind. They promise a future. She will be powerful. She won't have to hide.

Katrina Crane is tired of hiding.

What would you have me do?

SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS

Katrina leaves the battlefield and heads for the makeshift hospital. She feels numb, and slightly removed from the world, as though she's watching it through a window. But she is determined.

Reverend Walters, one of her coven, stops her before she can enter the building. "Mrs. Crane," he says, "Ichabod is… he's… he was wounded. He's dying. I'm not sure we can save him."

"Why not?" she whispers, her voice sounding weak with shock.

"When he killed the horseman, their bloodlines merged. If we save Ichabod, the horseman will be saved as well."

"So you want me to just let him die?" she asks, he voice cracking on the last word. She sounds half-mad with grief. She hadn't realized until now how good she was at lying. She pauses, pretending to think. "What if we put him to sleep, and the horseman as well? Then we'll figure out how to break the bond between them, and wake Ichabod up." The Reverend nods, once, and she turns away and runs into the hospital.

She sees Ichabod, lying on one of the dirty pallets on the floor, and runs to him. There are tears streaming down her cheeks, and they, at least, are real. In some deep corner of her mind, she's glad she's still able to grieve.

The Reverend walks up behind her and passes her a Bible. "We don't have much time," he whispers. She nods, places one hand on Ichabod's forehead, and begins the spell.

The panicked look in Ichabod's eyes just before he stops breathing will haunt her for months to come.

SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS

Katrina spends months preparing the spell that will break the bond between Ichabod and the horseman. The spell that will free the horseman from his grave.

It is the spell that will kill Ichabod Crane, for good this time, but she doesn't allow herself to think that.

She stands at Ichabod's grave. She is ready. She has to do this. If she does this, she will be powerful. There will be no more witch hunts. She will be safe.

She has just begun the spell when the Reverend and the rest of her coven enter the cave.

They trap Katrina's soul on another plane. Then they lead her home. Her body is still here, living and breathing, even if her mind is gone. They feel guilty about it, but what else were they to do? She'd made a deal with Death.

SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS

Hours pass. Or maybe years pass, she can't really tell.

And suddenly, Ichabod is there.

"I'm sorry, my love," she says.

It's true.

She is sorry.

But the horseman has promised her the world.