It didn’t make sense. She didn’t believe it was real – she wouldn’t believe it. It couldn’t mean what she thought. It couldn’t be that. And yet – that was the only conclusion to draw, no matter how unacceptable or nonsensical – or terrifying.

Edward Fosca had written it – this hellish love letter – and he had written it to Zoe.

Mariana shook her head. No – not Zoe, her Zoe. She didn’t believe it – she didn’t believe Zoe could possibly be involved with that monster …

Then she suddenly remembered that strange look on Zoe’s face – staring at Fosca across the courtyard. A look Mariana had taken for fear. What if it was something more complicated?

What if, from the very start, Mariana had been seeing everything from the wrong angle, looking at it from the wrong way up? What if—

Footsteps – coming up the stairs.

Mariana froze. She didn’t know what to do – she must say something, do something. But not now, not like this; she had to think first.

She grabbed the letter and stuffed it in her pocket, just as Zoe appeared at the door.

‘Sorry, Mariana. I was as quick as I could.’

Zoe gave her a smile as she entered the room. Her cheeks were flushed, and her hair was wet. She was in a dressing gown and clutching a couple of towels. ‘Let me just get dressed. One sec.’

Mariana didn’t say anything. Zoe put on some clothes, and that quick flash of nakedness – that young, smooth skin – reminded Mariana for a second of the beautiful baby girl she had loved, that beautiful, innocent child. Where had she gone? What happened?

Tears came into her eyes, but not sentimental tears; tears of anguish, of physical pain – as if someone had slapped her face. She turned away so Zoe wouldn’t see, and hastily wiped her eyes.

‘I’m ready,’ said Zoe. ‘Shall we go?’

‘Go?’ Mariana looked at her blankly. ‘Where?’

‘To the folly, of course. To look for the knife.’

‘What? Oh …’

Zoe looked at her with surprise. ‘Are you alright?’

Mariana slowly nodded. All hopes of escape, all thoughts of fleeing to London with Zoe, had faded from her mind. There was nowhere to go, nowhere to run. Not any more.

‘Okay,’ she said.

And like a sleepwalker, Mariana followed Zoe down the stairs and across the courtyard. It had stopped raining; the sky was leaden, and oppressive charcoal clouds swarmed above their heads, twisting and turning in the breeze.

Zoe glanced at her. ‘We should go by the river. It’s the easiest way.’

Mariana didn’t say anything, just gave a brief nod.

‘I can punt,’ Zoe said. ‘I’m not as good as Sebastian was, but I’m not bad.’

Mariana nodded, and followed her to the river.

Outside the boathouse, seven punts were creaking in the water, chained to the bank. Zoe took one of the poles resting against the boathouse wall. She waited for Mariana to climb into a punt, then loosened the heavy chain securing it to the bank.

Mariana sat on the low wooden seat; it was damp from the rain, but she barely noticed that.

‘This won’t take long,’ Zoe said as she pushed them away from the bank with the pole. Then she raised the pole high in the air, plunged it into the water, and began their journey.

They weren’t alone; Mariana knew that right from the start. She could sense they were being followed. She resisted the temptation to look over her shoulder. But when she finally did turn her head, just as she expected, she briefly glimpsed the figure of a man in the distance, vanishing behind a tree.

But Mariana decided she must be imagining things. Because it wasn’t who she was expecting to see – it wasn’t Edward Fosca.

It was Fred.

7

As Zoe had predicted, they made fast progress. They soon left the colleges behind, and were surrounded by open fields on either side of the river – a natural landscape that had survived unchanged for centuries.

On the grassland, there were some black cows grazing. There was a smell of dampness and mouldering oak, wet mud. And Mariana could smell smoke from a bonfire somewhere, a musty smell of damp leaves burning.

A thin layer of mist was rising up from the river, and it swirled around Zoe as she punted. She was so beautiful standing there, her hair blowing in the breeze, that faraway look in her eyes. She resembled the Lady of Shalott on her doomed, final journey along the river.

Mariana was trying to think, but she was finding it difficult. And with each muffled thud of the pole on the riverbed, and each sudden rush forward of the punt on the surface of the water, she knew time was running out. Soon they would be at the folly.

And then what?

She could feel the letter burning in her pocket – she knew she needed to make sense of it.

But she must be wrong. She had to be.

‘You’re being very quiet,’ Zoe said. ‘What’s on your mind?’

Mariana looked up. She tried to speak, but couldn’t find her voice. She shook her head and shrugged. ‘Nothing.’

‘We’ll be there soon.’ Zoe pointed towards the bend in the river.

Mariana turned and looked. ‘Oh—’

To her surprise, a swan had appeared in the water. It glided effortlessly towards her, its dirty white feathers rippling gently in the breeze. As it neared the punt, the swan turned its long head and looked directly at her. Its black eyes stared into hers.

And a shiver ran down Mariana’s spine. She looked away.

When she looked back, the swan had vanished.

‘We’re here,’ Zoe said. ‘Look.’

Mariana saw the folly, on the bank of the river. It wasn’t a large structure – four stone columns supporting a sloping roof. Originally white, it had been discoloured by two centuries of relentless rain and wind, staining it gold and green with rust and algae.

It was an eerie location for the folly – alone, by the water’s edge, surrounded by a woodland and marsh. Zoe and Mariana sailed past it, past the wild irises growing in the water, and the rambling roses covered in thorns, blocking the path.

Zoe guided the punt to the bank. She wedged the pole deep into the mud of the riverbed, mooring the punt, pinning it against the river’s edge.

Zoe climbed onto the bank – and held out her hand to help Mariana. But Mariana didn’t take her hand. She couldn’t bear to touch her.

‘Are you sure you’re okay?’ said Zoe. ‘You’re being so weird.’

Mariana didn’t reply. She clambered out of the punt, onto the grassy bank, and followed Zoe over to the folly.

She paused outside and looked up at it.

It had a coat of arms above the entrance, carved in stone – the emblem of a swan in a storm.

Mariana froze when she saw that. She stared at it for a second.

But then she kept going.

She followed Zoe inside.

8

Inside the folly, there were two windows in the stone wall, looking out onto the river, and a stone window seat. Zoe pointed through the window, at the green woodland in the near distance.

‘They found Tara’s body over there – through the trees, by the marsh. I’ll show you.’ Then she knelt down, and looked under the seat. ‘And this is where he put the knife. In here—’

Zoe slid her arm into a space between two stone slabs. And she smiled.

‘Aha.’

Zoe withdrew her hand – and she was clutching a knife. It was about eight inches long. It was stained slightly with red rust – or dried blood.

Mariana watched Zoe grip it by the handle; she held it with a sense of familiarity – and then she stood up, turned the knife towards Mariana.

She pointed the blade directly at her. She stared at Mariana without blinking, her blue eyes radiating darkness.

‘Come on,’ she said. ‘We’re going for a walk.’

‘What?’

‘That way – through the trees. Let’s go.’

‘Wait. Stop.’ Mariana shook her head. ‘This isn’t you.’

‘What?’

‘This isn’t you, Zoe. This is him.’

‘What are you talking about?’

‘Listen. I know. I found the letter.’

‘What letter?’

In response, Mariana took out the letter from her pocket. She unfolded it and showed it to Zoe.

‘This letter.’

Zoe didn’t speak for a second. She just stared at Mariana. No emotional reaction. Just a blank look.

‘You read it?’

‘I didn’t mean to find it. It was an accident—’

‘Did you read it?’

Mariana nodded and whispered, ‘Yes.’

There was a flash of fury in Zoe’s eyes. ‘You had no right!’

Mariana stared at her. ‘Zoe. I don’t understand. It – it doesn’t mean – it can’t possibly mean—’

‘What? What can’t it mean?’

Mariana struggled to find the words. ‘That you had something to do with these murders … That you and he … are somehow involved—’

‘He loved me. We loved each other—’

‘No, Zoe. This is important. I’m saying this because I love you. You are a victim here. Despite whatever you may think, it wasn’t love—’

Zoe tried to interrupt, but Mariana wouldn’t let her. She went on.

‘I know you don’t want to hear it. I know you think it was deeply romantic, but whatever he gave you, it was not love. Edward Fosca is not capable of love. He’s too damaged, too dangerous—’

‘Edward Fosca?’ Zoe stared at her with a look of astonishment. ‘You think Edward Fosca wrote the letter? – and that’s why I kept it safe, hidden in my room?’ She shook her head scornfully. ‘He didn’t write it.’