'Marie, do you happen to know where Papa is?'

Marie, who has remained on the constant cusp of bursting into tears ever since Mama passed, stares at me with wide water-brimmed eyes, twisting up her apron in her hands.

'The Admiral took himself off for a nap, Miss. He looks exhausted. He's really not himself. He wouldn't eat or drink a thing I offered after they came for dear Mrs. Elmes. I don't know what else to do!'

Before Marie can burst into actual tears, I grasp her hand to calm her. 'Fear not, Marie,' I say with a smile that I am sure looks as false and as hollow as my words sound. 'I am quite sure all the Admiral needs is some time. He will eat and drink again when he is in need of it.'

Marie nods dutifully, but I can see she is unconvinced. 'Miss, can I get you and Master William anything?' The poor lamb looks as if she is desperate to feed us, but the thought of eating anything in this moment makes my stomach churn with nausea.

I pat her hand. 'No, no, we are quite alright. Thank you, Marie. We will call for some supper at a later hour.'

Marie smiles at the idea she might be able to finally force one of us to eat something and leaves the hallway, sniffing as she goes.

I stand at the bottom of the staircase and strain to listen. The house is uncommonly quiet and my skin prickles with the ominous silence. William and I had returned, only to pass the black funeral carriage of Pugh & Sons Funeral Directors on the road, carrying Mama's coffin. Instead of Papa, Silas had been waiting, cap in hand, watching the funeral carriage as it trudged into the distance.

'The Admiral couldn't bear it no more, Miss,' he'd explained to me when I had enquired as to why Mama was being taken. 'Mr. Pugh will care for her now, until the service in two days hence.'

I suppose I could not blame Papa. After everything that had taken place here just the day before, I should imagine the idea of Mama residing alone in the parlour room with no mourners come to visit – for no one would surely come here now – had troubled Papa greatly.

Or mayhap he did not wish to look upon the face of the wife he killed?

I grimace, desperately trying to push that unwanted thought out of my head, for it pains me greatly to think that Papa had any part in this dark scheme. Sadly, however, the knowledge that Papa holds the box which the Sin-Eater's key would unlock troubles me more than I care to admit. I have no idea of the connection between the two men, but with Mr. Hemsby's account of the sinister they who plagued him with terror, the photograph of Papa and his friends at Rectory Wood and now, this mysterious key with the skull-like bow, doubt is sowing seeds of disquiet so deep that I think the roots will be bound around my skeleton for eternity.

'Psst, Lily, come now.'

William stands at the study door, gesturing for me to hurry.

The idea of stepping over the threshold into Papa's study fills me with utter dread, but I do regardless, following my brother into the darkened room. The drapes have been drawn almost fully closed until just a crack of harsh light pushes its way between the heavy velvet borders.

Dust dances in the air where the beam shines through and I can see Papa's bureau, usually so ordered and organised, in disarray. His favourite decanter sits on top of a stack of documents, a glass lying empty beside it. Papa is not often given to drink, usually only when he has company or at meal-times – not like his friend Mr. Darborough – and I am saddened to see it today, a pang of melancholy that I hastily suppress. All emotion must be swept aside if we are to continue in our mission, but it is so terribly hard because this is Papa we seek to investigate as if he is a man we do not know, and yet considering all the clues and all the terrible things I have seen an experienced, mayhap we do not know him after all.

I rush to pull open the drapes, desperate to allow the daylight to banish the gloomy air.

'Where is it?' I ask William, who stands in the middle of the room, looking quite lost.

He does not want to find the box. He does not want to open it, nor does he want to know what secrets it hides. I can see it in his eyes.

I cannot say I blame him. Secrets have a nasty way of unravelling the tightest and most secure of binds. Once you have picked at a loose thread, all can become undone, and I do not wish our family to unravel any more than it already has.

My brother moves to Papa's bureau and, retrieving the letter-opener that lays on top, he crouches in front of the small cupboard door and – much to my surprise – quickly manages to pick the lock and open it.

'William Elmes!' I say, astonished. 'When on Earth did you learn how to do that?'

'It may surprise you to know that I am quite skilled at endeavours other than just annoying you,' he says, with a grim smile.

'Of course, you are. I just never once imagined one of those skills would be picking locks.'

He glances at me, a glint of mischief in his expression. 'Picking locks, battling dark forces, and deciphering clues. We make quite the team. Perhaps we should start our very own detective agency?'

I purse my lips. 'I am not sure I can withstand much more adventure than this.'

Nor mortal danger.

'Done,' he says, opening the cupboard, and rummaging inside before standing, holding a small, ebonised box which he gingerly places on the bureau.

I move to his side and for a moment, we do nothing but stare at the box, almost as if it is a viper coiled and ready to attack us if we dare move but a millimetre.

The box is no bigger than a cigar box or tea caddy, with a dark red paint and brass inlay decorating the lid and an intricately carved border. The skull-patterned lock is an exact replica of the pattern on the bow of the tiny key we had found at the Sin-Eater's house.

'Well, goodness,' I finally say, exhaling deep. 'We cannot simply stand here staring at the blasted thing. We came here to open it and open it we shall.'

Taking the key from William, I insert it into the keyhole and turn until it clicks. Swallowing hard, I lift the lid. Inside, the box contains several small, opened letters, bound neatly together with red string, a silver locket on a long chain and a magnifying glass with an ornate burnished handle.

'This was Grand-Mama's,' I say, gesturing to the magnifying glass. 'And the locket too, I think.'

William picks up the bound letters, studying the italicised script. 'This is Grand-Papa's writing, I am sure of it.' Carefully untying the string, he opens one letter and nods, wrinkling his nose. 'I was right. Love letters to Grand-Mama.'

I grab it from his hand, shaking my head at his distaste as I scan the letter. 'Well, I think it's rather charming. Mayhap you can learn something, dear brother, if you wish to win the affections of Jenny Darborough.'

William preens. 'Oh, those are already won, trust me.' He sighs, frustration marring his brow. 'This is all well and good, Lily, but why on Earth would the Sin-Eater hold the key to a box containing soppy letters belonging to our grandparents?'

'Hmm,' I ponder. 'Unless it is only meant to look like a box of sentimental things?'

Picking up the box, I close the lid and tip it upside down, seeing nothing of interest underneath. I study each side intently, before placing it back on the surface and examining the inside again. Unsatisfied, I remove all the contents, close the lid again and lift it close to my ear, giving it a small shake. Something rattles inside the empty box.

William and I stare at each other wide-eyed.

'Quick, the letter-opener!'

Taking the sharp blade, I slice along velvet inlay around all four sides, before carefully prising the inner compartment from the shell of the box.

A black silk drawstring bag sits in the hidden space concealed by the inner compartment which is notably shallower than the box itself.

My alarmed heart picks up a beat.

Retrieving the bag, I loosen the strings and reach inside, pulling out a tiny, corked glass vial, almost dropping it when I spy the dark red liquid it contains.

'Heavens, Lillian, please say that isn't what I think it is?'

'If you are wondering if it is blood,' a deep voice rumbles from the doorway, 'then you would be correct in your assumption.'

We both look up in fright, and I almost drop the vial then, just managing to catch it before it can slip through my fingers and clatters onto the bureau.

Papa fills the doorway to his study, looking, not furious and terrifying as I expect him to be, but utterly drained and exhausted, his eyes full of pain, his skin sallow and drawn.

'Papa...' I begin to say, but he stills me with a gesture of his hand and gently closes the door behind him.

With his whole body trembling, William steps in front of me, doing his utmost to puff out his chest in a show of bravado.

'D-do not come any closer, Papa!' he warns, quickly grabbing the letter opener and brandishing it in front of him, albeit in a very shaky manner. 'You might be an Admiral, but I am younger and quicker and will defend us both till the death!'

'William!' I gasp. 'What on Earth are you doing?'

'I will not let him harm us, Lily. I will do whatever it takes!'

Papa rocks back on his heels as if William has indeed cut him with the blade. His face drains, his mouth drops open.

'Do you honestly think I could ever harm even a hair on either of your heads?' he croaks.

'Quite frankly, Papa, we do not know what you might be capable of! Lily and I went to Daniel's cottage. We read Joseph Hemsby's journal and he was talking about all manner of terrible things. About how Edna Bates was murdered. About how someone threatened him. We were threatened too! Something there tried to kill us, Papa! And then we find the key to this box – a box that you have in your possession, and now you are telling us this vial contains blood? What are we to think, Papa? Tell us!'

Papa crumples then, grabbing hold of the nearest armchair and collapsing into it and clutching his head in his hands. He does not move nor look up, but I have never seen him in such a state. My heart weakens for him, for the man who has been my life-long anchor, steadying this family through the stormiest of seas.

'Papa?' I say, taking a step forward but William grabs me, holding me back.

'Stop, Lily!' he hisses. 'Remember Joseph's warnings about the Devil!'

Papa looks up, his gaze sharpening. 'You think me to be the Devil?'

William frowns. 'The Rector says the Devil comes in many forms. He wears the face of those you love to fool you. He is a trickster. A deceiver!'

'Yes, he is that and more besides, but I am not he!' Papa says. 'The only evil in this room is in that very vial you hold, Lillian.'

I look down at the small bottle in my hand, wishing so very dearly I could put it down, as if whatever evil lurks within might seep through the glass and bury under my flesh.

'Whose blood is this, Papa? Tell us now and swear on Mama's soul that you will only tell us the truth!'

Papa looks at me, his eyes wide and red-rimmed. 'I swear to you on her soul. I swear to you on the way she took my breath away the first time I ever laid eyes upon her. I swear to you on my oath to her as we were married. I swear to you on my love for her, the strongest love that could ever be, rivalled only by our love for you both.'

Even William looks to waver, hearing Papa's heart break with every single word he utters.

'Go on, then,' I say. 'Speak it.'

Papa deflates a little in the chair. He appears older suddenly, as if something drains on his energy, leeching vigour and strength from his body before our very eyes.

'There was always something different about that boy,' he starts, fixing his gaze ahead, his eyes glazing over as if it is something else he sees in front of him, and not this room nor his children. 'Something peculiar. He was always an odd child, indifferent to everything and everyone around him. Nothing seemed to hold his interest or bring him joy. It was clear to see how people could sense the strangeness about him. How they would draw away from him and do their best not to look at him. He made people... uncomfortable. Uneasy. I have known adults to silence a room upon entry, but a child?'

Papa rubs at his temple, his brow knitted fiercely. 'I admit, at first, I felt sorry for the boy. He had no one. No friends. He was sickly and weak, and it was said he suffered the most excruciating night terrors. I could not imagine how frightening that must have been, and him, only a child. He would wake, screaming, terrified by what he had seen. He said that invisible creatures visited him at night, clawing at the coverlets of his bed, whispering terrible things in his ear. Of course, Dr Benedict tried to treat him, but just when we thought that his condition had improved, the chanting began.'

'Chanting?' I say. A coldness creeps over my skin. Slithers.

Papa nods. 'Yes. He would whisper the most terrible things under his breath. Chanting the same thing over and over.'

I pawn my own soul; I pawn my own soul.

I look down again at the vial of blood in my hand.

No. It cannot be. It cannot be his.

'He would be asked to stop,' Papa continues, 'and he would look at you as if you were quite mad, as if it were in your imagination and not real at all, but then he would smile, and you would know... you would just know.'

'Know what, Papa?' William asks.

'Why, that he enjoyed it, of course,' Papa replies, his face haunted with some dreadful memory. 'In fact, the child revelled in it. He knew what people thought of him. He knew the unease he created and yet he did not care. Even now, he does not care, although he makes a good pretence of it!' Papa sneers with disdain. 'He thinks he can walk among us, as if he is the same as us, but no more!'

I see the boy, now looking directly at me, his face a cold hard mask that reminds me of the dead, and his lips move as if he is chanting something under his breath.

The breath seems to leave my body as quick as the winds race from the mouth of the Mynd. The thought of it – the very thought of it – fills me with such dread and cold that I must lean against the edge of the bureau for fear the strength in my legs may fail me. The idea that I have got this all so very wrong pains me more than I could ever say.

After everything Mama had told me. After the lengths she had gone to in order to warn me of the whispering boy.

Had I really allowed myself to be manipulated so?

Have I really fallen in love with the Devil himself?