She waited in the middle of the room, arms folded across her tiny chest. The yellow in the dress was so intense he was sure it must be visible from the street through the haze of the lace curtains. Every second counted, but now that she was here inside his flat he was not sure what to do next.

'What are you looking at?' She glanced down at the front of her dress. 'Is there something on it? I hope there's not a stain.'        

'Your dress is perfect.' He went to the fridge in the corner, squatted down and looked inside, eyes still throbbing from the yellow. 'I only have milk,' he said.

'I can't drink milk. I'm allergic. Don't you have anything else?'

He felt her coming closer. There was nothing else to drink. The fridge was as good as bare.

'You must have water,' she said.

He stood up and rinsed out a glass under the tap. All the while she watched him as if he were performing a rite.

'Is this your living room or your kitchen?' she asked.

'Both.'

'That's a funny kind of room.'

She fell silent and he saw that she was looking at his cluttered desk in the corner next to the bay window and at the tall bookcase standing beside it.

'Are you a teacher?'

He shook his head.

'Then why do you have so many books?'

'They're for my work.' He handed the glass of water to her and listened to her gulping it down and gasping between mouthfuls. He kept his eyes off the dress but he could feel it there, warm and flourishing. When he saw the dress again it was through the thickness of the emptied glass she held up to him and for a moment it seemed he had the colour he needed captive in his hand. He rinsed out the glass and stood it on the rack to dry, then he rubbed his eyes with the sleeve of his jacket.

'What's the matter?' she asked.

'Nothing. Just my eyes. They're tired.' Still facing the sink, he said, 'You can sit over there on the couch, if you like.'

He heard the tough old leather creaking as she took her place. And when he looked at her again the dress had become very ruffled and the yellow seemed concentrated in the creases around her hips.

'I'm going to be a ballet dancer when I'm big,' she said. She had her small shoulders pressed against the backrest and her thin legs were stretched out in front. She bobbed her sandaled feet up and down over the edge of the cushion. 'I go to lessons every week.'

He sat down at his desk and rotated the chair so that he was facing her, but he could look at her directly for only brief moments.

'Do you like my dress?'

He turned quickly to the window, cheeks burning, and did not reply.

'You keep staring at it.'

Awkwardly, as if the question were an obscene one, he asked, 'What colour is it?'

She looked down at the hem and then gave him a mischievous smile. 'Are you trying to trick me?'

He told her no and to give himself chance to think he began to close and tidy the books that were spread across his desk. He paused at one whose pages he'd heavily annotated. It was a volume of John Stuart Mill's collected works and contained an account of the author's experience of profound melancholy during the winter of 1826. It seemed an age had gone by since he'd first stumbled across this writing.

'It was a birthday present,' she said.

His eyes were drawn to her against his will and the yellow shone at him with such brilliance it rang in his ears. He watched as she slid herself forward to the edge of the cushion and rested her palms on her bare knees. The toes of her sandals touched the floor and she rocked herself back and forth restlessly. 'I think it's time for me to go.'

He sprung up from the chair. But when he saw how frightened she was he stopped and let his arms fall down by his side. He spoke in his kindest voice. 'Stay for another drink. I think I have some juice.' He went over to his fridge and scanned the empty shelves. If not juice, then what could he give her to make her stay a little longer until he had the courage to act? He looked about his room, from wall to wall, despairing. There was nothing; he had nothing, not even a TV or a radio he could switch on for her.

'I mustn't be late,' she said, as if to herself. 'If I'm late, I'll get into trouble.'

He felt the house keys inside his pocket and his thoughts moved in a new direction. It was not the girl that had to stay - just the dress. He could request a small part of it, maybe? A few inches cut from along the hem? He had money to pay for it - a fair exchange. Within his reach hung a pair of kitchen scissors he used for trimming meat. His fingers curled as he imagined kneeling before her with permission to take what he needed.

She stood up from the couch and straightened the dress, making ready to go.

He reacted quickly, placing himself between her and the open living room door.  'Stay,' he said.

'But I have to go to the toilet.'

It was not the girl or even the dress he needed - just this uncompromising yellow.

'The toilet,' she said again and shivered. 'I'm bursting.'

He let her go past him into the hall and followed her closely to the bathroom door. She opened it with a slow, exploratory push and then reached up a hand to the dangling pull-cord. Before the light came on he turned his head away, afraid to see too nakedly the rebounding sameness of dress and walls. But as soon as the door closed he regretted it. He took hold of the handle. There was no lock on the inside . . . just one turn . . . it was his bathroom . . . his yellow to see. But he could not make himself open the door. He pressed his ear to it instead and listened hard. All he could hear inside was the dull roar of the fan.

He returned to the kitchen and lifted the scissors from the hanging rack on the wall. He tested their sharpness by cutting into an old cloth he kept for wiping his hands. Satisfied, he took his wallet from his jacket pocket. He still had the money he'd withdrawn for the paint - more than enough to buy the whole dress, he thought. He sat on his chair and waited, playing agitatedly with the scissors. For a while he stared out into the street through the white blur of the lace curtains, then he turned around to his desk, where John Stuart Mill lay open before him.

At these very pages, in the depths of Mill's melancholia, his work had come to a standstill; or rather it had expanded to incorporate a study of Romanticism, modern philosophy and the German language, without bringing him a step closer to what he had come to this flat to achieve. And it was all due to Mill's slapdash transcription of a quotation by Goethe about Schiller. Not only had Mill used the adjective fürchtlich instead of furchtbar, he had also substituted Fortschreitung for Fortschreiten. Yet this lack of identity was only the beginning of the problem. Goethe's praise of his younger friend Schiller's 'tremendous progress' had been expressed to the composer Felix Mendelssohn, who had subsequently reported Goethe's words to the translator Sarah Austin, and it was she who had first made them public. Nothing he read anywhere had led to the discovery of Goethe's original words or allowed them to be inferred. They were lost for ever, unobtainable - if indeed they had ever been spoken at all. Faced with Schiller's tremendous progress, his own work had lost its way.

A clamour from out in the hall roused him. It continued for several seconds before he grasped what was happening. Only rarely did he hear the sound of his door bell. From its box above the door it could make the whole flat recoil. It shrieked again, even more insistently. Usually he would try to ignore it, but now, panicking about the girl, he rushed out into the hall, scissors in his hand.

The bathroom door was still closed and when he put his ear against it he could hear nothing but the fan. He looked up at the grey box as the bell sounded a third time. He could see no wires to cut and while the shrieking continued he took out his keys and unlocked the door. Occasionally a courier would disturb him like this, determined to drop off a package for one of the other flats, or else it would be a religious enthusiast keen to talk about his soul.

He walked cautiously toward the front door, trying to see the caller through the narrow stained-glass panels. The mosaic patterns were deeply coloured and layered with dust and revealed only the dark, blurry outline of a figure. When he pulled open the door he saw immediately there were two of them - police officers, in heavy uniforms, a male and a female. They pressed toward him.

'We're looking for a missing child,' said the male officer.

'We need to come in,' his colleague said and put a hand on the door.

He stepped back helplessly and allowed them into the hall. The male officer removed his hat and held it at his side. The female reached into a hip pouch next to where her handcuffs hung.

'This is the girl we're searching for,' she said, handing him a flyer. She watched his face as he looked at it. 'Have you seen her?'

'No,' he said, shaking his head. He tried to give the flyer back to her but her hand stayed down by her side.

The male officer went to the letter rack mounted on the wall. Some of the compartments where crammed full and on the carpet below was a mess of old junk mail, litter and cobwebs. 'How many flats are there in this building?'

'Six.' But he had never really been sure. 'Or maybe seven.'

'Are all of them occupied?'

'I think so.'

'I take it that one there is yours?' The door to his flat was slightly ajar. 'Could we go inside for a moment?'

He considered saying no, that they had no right to enter his flat, but he knew it would only make them more suspicious. So he put on a willing smile and ushered them quickly through his hall into the living room. They stood with their backs to the window and their padded uniformed bodies made the room feel crowded. He invited them to sit down on the couch but they both refused and remained standing side by side. The female officer's attention was drawn to the single glass, upturned in the dishrack on the draining board.

'Do you live here alone?' she asked him.

'Yes.'

'Are you here alone at the moment?'

'Yes,' he said again, 'just me and my books.' But he was thinking at every moment of the girl in the bathroom. How much longer before she came out and betrayed him? Coughing, hand over mouth, he looked at the male officer who had begun to speak.

'Were you about to go out somewhere?'

He coughed again, confused, and shook his head. 

'You have your jacket on.'

Yes, he did - he became aware of it all of a sudden, felt it squeezing under his armpits. Now they took him for a liar, a man with secrets, things to hide. 'I went out to buy some paint,' he said, looking back and forth between their young doubting faces. 'For decorating.'

The male officer scanned the bare walls and asked: 'What time did you return?'

He couldn't remember. Many hours seemed to have passed since he'd brought the girl into this room. Yet he was still wearing his jacket. 'Just now,' he said. 'I've just got back now.'

'We think the girl came along this road so we're calling at every house. Anything you saw might be important.'

He opened up the flyer, which he'd folded several times without being aware of it, and looked down at the face on the picture. But instead of focusing on its features he imagined the yellow dress, like a beacon, bringing all the residents to their widows.

'If you do remember anything call that number at the bottom.'

They started to leave and, as he followed them out of the living room into the hall, the male officer who was leading asked, without turning around: 'Did you buy any paint?'

'I couldn't find the right colour.'

'Getting it right is very important. You need a colour you can live with.' He stopped before the bedroom door, which was not firmly shut. 'May I?' he said, and without waiting for an answer he opened it wide enough to be able to peer inside, into all the corners of the room. He even bent his knees to get a clear view under the bed. At the same moment the female officer seized the handle of the bathroom door.

'What's in here?' she demanded.

'Just the bathroom,' he said, shrinking back into the corner of his hallway.

She shoved open the door, took a step forward and then gave a small cry. The male officer sprung away from the bedroom and pressed behind her, hand on baton. Their dark, uniformed bodies filled the entire doorway and the only sound came from the toiling fan.

He felt for the kitchen scissors inside his back pocket and kept his hand on them ready to defend himself. He had only ever wanted a matching yellow for his bathroom and to be able to continue his work. But they would interpret it differently, as a crime of some kind. The officers turned around together, like synchronised puppets. Their faces looked ravaged. The male officer opened his mouth to speak but in the end he just shook his head. The female pushed past him, dragged open the flat door and staggered out into the communal hall shouting 'Jesus, fuck!' He gripped the scissors as the male officer swayed toward him but the much bigger man flattened him against the wall before he could use them. Long moments passed with them both pressed together. Winded and growing faint he thought about the girl and the dress, and he pictured the tautology of yellows he had finally achieved. The officer gradually pulled himself upright again, freeing him, and muttered an apology. He picked up the hat he'd dropped and left the flat, closing the door hard behind him.

He went into the bathroom. The bare patch near the toilet was gone. Only the glinting wetness of the paint betrayed where it had once been. He flushed the toilet, then lowered the lid and sat down on it. He could not understand what had caused the officers to take such offence. But then he dimly recalled his own reaction when he'd first been shown this bathroom all those years ago - it had started in his stomach, a feeling of nausea and dismay and within seconds he'd wanted to scream for his life. The landlord had even offered to have the walls repainted for him; but eager to be left alone to begin his work he'd swallowed hard and shaken his head. It took time to grow used to this yellow.

He decided that the girl must have crept out while they were all talking in the living room. He unfolded the flyer again and studying the photograph he tried to determine if this was the same girl. He hardly noticed faces anymore, especially children's faces - they all appeared as one to him, small, and innocent perhaps, a thing disconnected from his work. The girl's name and age were on the flyer, as well as a short description of what she'd been wearing when she'd left home. He read the description carefully, as carefully as he read the words in his books, until he was sure what it said. He began to feel safe again. The police were searching for a different girl, a girl in a dress that was red.

Above his head the fan clattered a few times amid its roaring, urging him back to his desk to finish his work.