What if they don't get rid of the ghost? What can he do to them? How about a plea or an anxious request?

No. He's got money, pull, position; trust me, this dude is scary and arrogant, and he really doesn't make anxious requests. He knows most of the club owners and most of the money people in the industry and he can seriously impact them. Luckily, by and large, he's not an asshole, but he's autocratic and used to issuing ultimatums.

I don't think you should give away the "political cover-up" part of the plot, because you want to keep the element of surprise.

Good point. It also sounds weirdly modern in regards to ghosts, but that could be a useful point if you want to explore how people don't change as much as you'd think over time.

"And as the Festival disintegrates around them, Ringan and Penny begin to suspect that Lady Susanna's death was not as simple as they've been told, and that the truth may expose a four-hundred-year-old lie with implications far greater than a husband's betrayal..."

ooooooooooooh! I like. May I use?

edit: connie, yep, I agree. The cover-up political thing is a giveaway. Will remove.

May I use?

That's what it's there for, babe.

he's autocratic and used to issuing ultimatums

How about "demands" instead of "ultimatum"? Let the story show that it's more of a threat instead of just "Do this, peasant."

Hmmm. There's one thing in this:

"And as the Festival disintegrates around them, Ringan and Penny begin to suspect that Lady Susanna's death was not as simple as they've been told

that I think I need to change: it should be something about not being as simple or as straightforward as the song lyric suggests. IOW, I need to tie it into the song, which is the title.

For Ringan and Penny, though, there's a downside: Callowen is haunted, by the pretty young wife of a 17th century Leight-Arnold, killed by her husband when she's caught in bed with another man. What's more, her story is told in a famous traditional song, "Matty Groves". And the couple has already held two terrifying exorcisms for ghosts whose stories, true or false, are told in songs.

This time, it seems, there's no mystery for them to solve; the Lady Susanna's story is straightforward, and besides, Miles Leight-Arnold is very proud of his family phantom.

A few suggestions for clarity, mainly reorganizing your sentences:

For Ringan and Penny, though, there's a downside. The couple has already held two terrifying exorcisms for ghosts whose stories, true or false, are told in songs. And Callowen is haunted, by the pretty young wife of a 17th century Leight-Arnold, killed by her husband when she's caught in bed with another man. What's more, her story is told in a famous traditional song, "Matty Groves".

This time, it seems there's no mystery for them to solve; the Lady Susanna's story is straightforward, and besides, Miles Leight-Arnold is very proud of his family phantom. But from the first night, it becomes clear that Lady Susanna, harmless and tragic, is not the only spectre.

Something else is awake, moving through walls and nightmares, growing stronger as it feeds on Penny's sensitivity and on the very fear it creates: Andrew Leight, a man as twisted and violent in life as he is in death. When Penny is attacked and Charlotte, the daughter of the house, is injured, Lord Callowen gives Ringan and Penny an ultimatum: get rid of Andrew Leight, but leave Lady Susanna's ghost untouched.

But I like Amy's suggestions even better.

Bev, niiiiiiiiiiiice.

Damn. My brain is backstage at Madison Square Garden right now, not in Hampshire. Very tricky trying to focus.

Actually, I want to use yours, end it with Amy's, and take part of connie's suggestion about the Callowen info. Gimme a minute...

edit: except "spectre". I hate that word, and never use it.

Well, I take issue with the fact that Susannah isn't "alone." I don't think she IS with Andrew. I'm not overly fond of spectre, it just wasn't ghost again.