Caroline focuses on the portrait behind the Headmaster. Another livid face with a vanity of whiskers that looks unimpressed to see her back in this study. Three times in as many months, to speak about the same pupil. Always rebuffed with the implication that, as Belfin’s first female teacher, she is unable to cope with the school’s standards.

‘This isn’t an academic matter.’ Eerie echoes follow her words across the cavernous room. Breathe. Stay strong. Blake Wentworth needs help. ‘My concern for the boy is pastoral.’

‘Enlighten me, Miss Frame. In haste, if you would, the hour is late.’

Why does he still feign ignorance? ‘It’s a question of his wellbeing. As you know, Wentworth has developed an unhealthy obsession with the water woman.’ A bone-pale figure with dripping, waist-length hair, believed to haunt the lake they call Silent Pool. In local folklore, she’s the ghost of a village maid who swam there. Until she was seen by six of the King’s soldiers, who stole her clothes. When she refused to leave the water for their entertainment, they waited, watching, until she drowned.

Pressing his fingertips together, the Headmaster leans back against his chair and looks at her as though he is considering a punishment. ‘The Silent Pool has captured the imaginations of Belfin boys for hundreds of years. It’s part of our heritage.’

Of course. The boys draw the woman endlessly, sitting on the bank or drifting through the wooded copse. Always naked, pleading. Sometimes with a half-dozen furtive faces peeping through trees. The Head of Art calls it a sign of maturity, addressing the latent misogyny of the tale. Caroline sees only the strange enchantment of the breasts and bare flesh, long limbs touched by moonlight. Poetic licence. In the story she never steps out of the water, although Caroline is convinced that she leaves it now.

‘I am well aware of that.’ As the Fourth Form cross-country skirts the lake, every new boy stops to read the sign with its picture of a blushing, half-bare maiden. By the time they return to top pitch, sweating and muddy, the legend is firmly lodged in their minds as something special to Belfin. Their ghost. Whispered in dorm rooms, torches under chins, tucked up in blankets. There is always one who takes it too far, frightening the others to tears and sleepless nights. By the time the year is out, the boys are more interested in the picture than the story. Except Wentworth.

‘Other schools have their ghosts. The headless rider of Alford, the black dog at Charlton. Musters has a grey lady, mother of the first Warden.’ He pulls at the collar of his gown. ‘Need I continue?’

A violated woman isn’t something to be prized, to gain membership of an exclusive circle. The thought remains unspoken. Caroline pushes her fingernails into the flesh of her palm, counts to six, thinks of the dreadful signs. Each morning there are long, dark hairs across Blake’s pillow, wet footprints that she cannot wipe away and which finally disappear in daylight. Evidence that the Deputies refuse to acknowledge. ‘Blake has been found several times walking to the lake alone. After dusk. Once after lights out. As his tutor, I’m concerned that he might choose to hurt himself. His thoughts are increasingly morbid, he’s frightened of his father and he misses…’

‘The tale is harmless, Miss Frame. Wentworth is an unpopular boy who is grieving the death of his mother.’

Exactly. He is vulnerable. Ripe for the taking. And something is out there. Something malevolent. Vengeful. A revenant presence she can feel like a threat and which seems, somehow, to cling to Blake. Drawn by his sadness. ‘It’s my duty to tell you if a pupil is in danger.’ Should she mention the Archives? A pattern of drowning. Five since records began and always boys who were bereaved, in low spirits, suggestible. ‘And I know that it isn’t the first time a boy has…’

‘Accidents. Nothing more.’ The Headmaster removes his pen lid, pulls up a sheaf of papers. Their interview is over. ‘Speak to Matron. Get him on extra sports, if you must, but I’m quite sure this will be the last of it.’

What did she expect? If only she had the authority to call his bully of a father and insist he is collected. Blake is in danger. The lake ghost moves closer. Caroline has taken to spending the night in a chair at the end of the dorm, poised to stop him leaving. Tonight she will do the same, though her eyes droop with weariness at the thought.

When she takes up her post, lights are already out in the junior corridor, tired bodies curled beneath blue blankets. Rising through the sweaty musk is another scent. Something new, like sulphur and moss. Rank damp permeates the air, clawing at her throat, setting her heart racing. Even before she pulls back the covers, she knows that Blake will not be there. A pair of pillows moulded in his place, strands of hair across the mound like tide-strewn seaweed. Below the bed is a puddle of water, the same strange green as the Silent Pool.

Wet grass soaks her slippers as she tracks his footprints across the lawn. Through the creeping dark of the copse and its startled scratching. The teeth and claws of night-time creatures. Mist gathers in twists as she reaches the lake, rising in shapes like dancing children, tricking her eyes. She is standing on top of the bank before she sees the two figures, already waist deep. Blake holds the hand of a bone-pale woman who pulls him gently forward, hair wrapped around his neck like a noose. Their eyes are shining, their expressions rapt. They do not hear Caroline calling. More silhouettes emerge from the water, soaked through, in thin cotton pyjamas. One by one they raise their arms. I’m quite sure this will be the last of it. Six boys. A retribution.