Running hurt but the old man had made it. He leant, gasping, in the burnt out doorway waiting for the boy. 'Hsst!'

His quarry turned warily to find an old man with a flat cap leaning in the entrance to one of the many derelict houses in the run-down street. 'Over here!' The old man straightened and gestured with his crutch and the younger man relaxed.

Harmless: the owner of Spinners' End's junkshop, 'the catman', was also the local lunatic. An injury he'd suffered while in the army made the locals more tolerant of the obvious mental problems.

'I've not seen your cat old man.'

'Cat's been dead years.' The old man seized the other's arm and scuffled him into the house. 'No lad.' The cloth cap was removed and twisted and replaced on his balding head. 'We need to talk. Come on.'

Crutch pumping, the catman set off at a fast hobble and the younger man followed. Through the burnt out shell of the dwelling they slipped, unobserved, down the rear garden and along the high walled, cobbled entry that ran between the backs of rows of houses. The old man unbolted a gate to where butterflies flitted over a narrow path that ran between crowded elderberry, buddleia and briar. In the gap between the outhouse and the wall, as the gate was locked behind them, the younger man stopped breathing; such was the stink of catpiss and filth from his companion. Thorns scratched at him as he followed into the kitchen at the rear of the house.

'Hang on while I inter the coat.' Beyond the kitchen, stairs led up from a small passageway on the opposite side of which the door to the junk shop lay open. Inside the shop, battered wardrobes and warped shelving obscured the street, a fifties Formica table supported a pile of vinyl records and dust overlay everything. 'Pretty eh?' said the old man. Scarred psychedelic paint on the inside of the under stair cupboard was all that remained of the shop's long ago heyday as a boutique. The door closed and the stench diminished noticeably.

While the old man's clothes were shabby to the extent of holes in the elbows of the red cardigan, they were clean. 'Practical invisibility for muggles, that coat. Not so much they don't see you as they don't want to.' The younger man froze and then drew his wand.

'Would you like some tea?'

There was no reply and the old man tried again. 'I've some reasonable scotch upstairs?' He limped back into the passageway and began, heavily, to climb the stairs.

Shutting the shop door behind him, wand in hand, the wizard followed him up.

The dark, curtained room at the front of the house contained a pair of wooden chairs with cushions and an old table that looked to have been part of stock. The mantelpiece of the small, boarded over fireplace supported a bottle of scotch, a bottle of pills, spectacles, a single glass and a novel by Le Carre. 'Sit down, son. I'll find another glass.' In the corner an old television appeared to be showing some sort of "Gritty Northern Drama". As it began to rain onscreen, there came the crash of thunder outside. The old man came back with a glass and a small jug of water just as an inversion of perspective revealed that the television was, in fact, showing the street by the patch of wasteland to which the wizard had apparated.

Behind the television, a lead ran into a cupboard built into the lower half of the right hand bay beside the chimney. The wizard hauled it open. He was no expert, but the muggle electronic equipment looked expensive. Very expensive. The old man knelt beside him and began to push buttons.

The television screen flickered and the picture showed Pettigrew standing outside number eight. It wasn't raining so this had to be a recording. As they watched, a scooter drew up at the kerb. 'Smith?'

'That's me.'

'Pepperoni pizza with . . . '

'Petrificus Totalis!' The deliver man remained frozen like a statue astride his scooter while Pettigrew took the box away and returned. 'Obliviate!' The pizza delivery man shook his head. 'Well?'

The man turned to find the pannier empty. 'I . . . I'm sorry . . . I don't know . . .'

'Must have fallen off. I suppose that happens sometimes. Look, don't worry about it. Next time, eh?' Pettigrew returned to the house. After a while the pizza delivery man rode away.

The screen went dark as the old man pushed another button and then closed the doors to the cupboard softly. 'Pettigrew's not there but Draco and his mother are in the house waiting for you and there's Aurors in number eleven, also waiting for you,' he said as he stood up. He picked up the bottle of scotch; opened it and part filled both glasses.

'Who are you?' demanded the wizard.

The old man swallowed his scotch, put the glass down on the table and took a deep breath. 'Many years ago I was married to a witch.' Severus stared at him. 'I didn't want to leave her. I was made to. Obliviated and . . .'

'Start at the beginning.'

Carefully the old man sat down.' I ran into her with a car,' he began. 'I was on my way . . .

In his mind the scene unfolds: a snowstorm, an exhausted young doctor on his way back from a house call and, suddenly, on the road in front of him a woman . . .

'Jonathan!' he calls, staggering through the snow with his victim in his arms, but his senior colleague has heard the car draw up and is waiting at the door. On such a terrible night he's been worried for his friend. 'She just appeared out of nowhere! I couldn't stop in time.'

He lowers her gently onto the couch in the sitting room. The electricity's out but oil lanterns reveal a dark haired girl: painfully thin, her fingers when she touches the young doctor's face are icy. 'Felix Felices,' she murmurs.

He takes her hand in his. 'My name is Tobias.'

The old man shook his head. 'It was my fault.'

'It was all my fault. Eileen was special. When I found out that she was a witch, well that just proved it but I . . . I had to have more. Eventually she gave in and took me to Diagon Ally. She took me into Eelops and Flourish and Blotts and we were eating ice-cream at Florean Fortescues when this woman came up and wanted to know who I was. Ministry of Magic, she said she was from. Said there were forms to be filled in. Didn't seem to think much of Eileen marrying a muggle. But we went and I, being the thrice damned, bloody, cursed fool that I was, I put down our address.'

'Two days later an owl arrived with the complimentary issue "The Prophet" sent to people who put notices in. There it was: notice of our marriage, courtesy of Dolores.' Mechanically, he swallowed some of his scotch. 'Eileen panicked.'

On a day in late summer they are waiting on the platform of the village station for the next train to anywhere. Their explanation of a belated honeymoon has been accepted but everything that they own of value is in the three suitcases at their feet. Eileen's face seems frozen. 'You worry too much,' he tells her.

In the hotel the next morning, while they are waiting for breakfast, he opens the paper to find, on page four, a report of an "unexploded bomb". Their small cottage is gone and they can't go back.

They take another train and another.

'I found work. We sold jewellery my mother had given Eileen and bought a house. We were happy.' A single tear flowed down the old man's cheek. 'When you showed first signs of magic at the age of four she brought you to the factory gate to meet me.' Slowly, Tobias curled up into himself, hiding his face behind closed fists and narrow wrists. 'We bought ice-cream on the way home.'

When the shaking had subsided, the old man unclenched himself. For a long time he stared at nothing and then he began again. 'When we got home her family were there. She'd this cat: scruffy, little, grey thing she'd took in. '

'Misty,' supplied Severus.

'Misty, aye. They turned her inside out and she was still alive and then they turned her back. She ran into a wall and, when I picked her up, she was dead.' Old fingers clutched the arms of the chair. Then they threatened to do the same to you and Eileen . . . she believed them. She signed the papers for divorce.'

'What did you tell the Ministry?'

'Nothing. They used something that sounded like 'Silence'. They just didn't want to listen. I woke up on the pavement of a strange town with no memory of the last seven years. The police were interested in what had happened to your mother but they couldn't find a body. They had to let me go. One of my old school friends pulled some strings and I joined the army. Drifted into the 'Dirty Tricks' end of things.'

'Intelligence work?' suggested Severus.

'You might call it that.' A wry smile accompanied a shake of the old man's head. 'And then some university kid on the fast track slipped up and there were consequences.' He tapped the crutch. 'Turned out the lad with the pipe bomb did me a favour though, because I remembered and when I got out of hospital, I came back here.'

Severus picked up the bottle and refilled the old man's glass. 'Tell me about the Aurors.'

'Three teams of two. Eight hour shifts starting noon. They check each shift for all sorts of things. Not for electronics though.' The old man took a deep breath. 'You'll need to take them out. You can get into the house through the loft. Rightly there should be fireproof partitions between all the houses but there aren't.'

'No questions?' enquired Severus, softly.

'I heard them discussing what happened. Seems to me that you had a choice: one life or many.'

'About my mother?'

'She's dead. She'd have to have been for you to have done something so stupid.' Tobias sighed. 'What could have persuaded you to join Voldemort?'

'When it became clear that I was to be his only heir, my grandfather took me under his wing. I was taught manners and a few other things and, at first, I welcomed the attention. My mother was a drudge who cleaned other peoples' floors and ignored me. Sometimes she seemed to hate me. Later, after I'd realised that I'd become something they used to punish and control her, I wondered if perhaps she did.'

'No, she wouldn't. But after what they did to the cat, perhaps she didn't dare . . .' Tobias got up and crossed the landing into the bedroom. Severus considered the bolted hatch from the landing to the attic.

'Here.' Old fingers held a miniature flask suspended from a silver chain in the manner of an old perfume bottle. 'Felix Felices. "Bottled luck",' she called it.

'You can't make luck,' said Severus absently. 'You can only borrow it.'

'And then you have to pay it back?' There was no reply and the old man's eyes closed for several moments. 'It's empty anyway but I thought you'd like to have it.' Tobias lifted the chain over Severus head. 'Those Aurors. One of them's got kids and the other's only a kid herself.'

'And both of them think me Evil incarnate.'

'The older one does. The kid's not so sure, but they're both as jumpy as hell so be careful.' Tobias tucked the chain into Severus' open necked shirt and rested his hands on his son's shoulders. 'People aren't good or evil. They're just people: someone's son or daughter. Once you forget that . . . It's only ever about people. The things people choose to do.'

Tobias turned and began to drag the small table towards the landing. Severus took it from him. 'Watch the woman,' said Tobias. 'If it'll help that boy of hers, she'll throw you to the wolves.'

'That, I knew.' Severus climbed onto the table, drew the bolts of the hatch to the loft and scrambled up into the darkness. 'Hang on,' said Tobias and disappeared into the bedroom. He hobbled back carrying something. Awkwardly, fingers curled around the bedroom doorframe, he scrambled onto the table. Leaning away from the long shadowy drop of the staircase, he held up a torch. Severus took it, switched it on and got his bearings in the cobwebbed darkness of the loft space around him. Finally, he glanced back down into the house.

'Good luck, son,' said Tobias.

Severus lifted the hatch door back into place.