Manhattan, with an east wind driving rain mixed with a little sleet along Park Avenue, was as bleak and uninviting as most great cities after midnight, especially in March. There was little traffic – the occasional limousine, the odd cab – hardly surprising at that time of the morning and with such uninviting weather.

In a stretch of mixed offices and residences, a woman waited in an archway, standing in the shadows, a wide-brimmed rain hat on her head and wearing a trenchcoat, the collar turned up. An umbrella was looped to her left wrist. She carried no purse or shoulder bag.

She felt for the gun in the right-hand pocket of her trench-coat, took it out and checked it expertly by feel. It was an unusual weapon, a Colt. 25 semiautomatic, eight shot, relatively small but deadly, especially with the silencer on the end. Some people might have thought it a woman's gun, but not when used with hollow-point cartridges. She replaced it in her pocket and looked out.

Slightly to her right on the other side of Park Avenue was a splendid townhouse. It was owned by Senator Michael Cohan, who was attending a fund-raiser at the Pierre, a function due to finish at midnight, which was why she waited here in the shadows with the intention, all things being equal, of leaving him dead on the pavement.

She heard the sound of voices, a drunken shout, and two young men came round the corner on the other side and started along the sidewalk. They were dressed in identical woollen hats, reefer coats and jeans, and they were drinking from cans. One of them, tall and bearded, stepped into the flooded gutter and kicked water, grinning, but as the rain increased, the other one wrapped his jacket tighter. Spotting the entrance to a covered alley, he swallowed the rest of his beer and dropped the can into the gutter.

'In here, man.' He ran for the entrance.

'Damn!' the woman said softly. The alley was next to Cohan's house.

There was nothing to be done. They had disappeared into the shadows, but she could hear them clearly, their laughter loud. She waited impatiently for them to move on, and then a young woman turned the same corner the men had come from and moved along the sidewalk. She was small, and, except for her umbrella, unsuitably dressed for such weather, in high heels and a black suit with a short skirt. She heard the raucous laughter, hesitated, then started past the alley.

A voice called, 'Hey, where are you going, baby?' And the bearded man stepped out, his friend following.

The girl started to hurry and the bearded man dashed after her and grabbed her arm. She dropped her umbrella and struggled and he slapped her across the face.

'Fight as much as you want, sweetheart. I like it.'

His friend grabbed her other arm. 'Come on, let's get her inside.'

The girl cried out in terror and the bearded one slapped her again. 'Now you be good.'

They dragged her into the alley. The older woman hesitated and then she heard a scream. 'Damn!' she said for the second time, stepped out into the rain and crossed over. It was dark in the alley, with only a little diffused light from the street lamp outside. The girl tried to struggle against the man holding her from behind, but the bearded man had a knife in his right hand and touched it to her cheek, drawing blood.

She cried out in pain and he said, 'I told you to be good.' He reached for the hem of her skirt and sliced upwards with the sharp blade, parting it. 'There you go, Freddy. Be my guest.'

A calm voice said, 'I don't think so.'

Freddy's face, as he looked beyond his friend, registered astonishment. 'Jesus!' he said.

The bearded man turned and found the woman standing in the alley entrance. She was carrying the rain hat in her right hand. Her hair was silvery white, highlighted by the back light from the street lamp. She looked to be in her sixties, but it was hard to tell anything about her face in the dark.

'What the hell is this?' the one holding the girl said.

'Just let her go.'

'I can't tell you what she wants, but I know what she's going to get,' the bearded man said to his friend. 'The same as this bitch. You feel like some company tonight, Grandma?'

He took a step forward and the woman shot him in the heart, firing through the rain hat, the sound muted. He was thrown against the wall, bounced off and fell on his back.

The girl was so terrified that she didn't utter a word. It was the man holding her who reacted. 'Jesus!' he moaned. 'Oh, God,' and then he took a knife from his pocket and sprang the blade. 'I'll cut her throat,' he said to the older woman, 'I swear it.'

The woman stood there, the Colt in her right hand, down against her thigh now. Her voice, when she spoke, was still calm and controlled. 'You never learn, you people, do you?'

Her hand swung up and she shot him between the eyes. He fell backwards. The girl leaned against the wall, breathing heavily, blood on her face. The woman removed her light woollen scarf and passed it across and the girl held it to her face. The woman leaned over, checked the bearded man first and then the other.

'Well, neither of these gentlemen will be bothering anyone again.'

The girl exploded. 'The bastards.' She kicked the bearded man. 'If you hadn't come along…' She shuddered. 'I hope they rot in hell.'

'It's a strong possibility,' the woman said. 'Do you live near here?'

'About twenty blocks. I was having dinner at a place around the corner, had a fight with my date and walked out hoping to find a cab.'

'You never can find one when it's raining. Let me look at your face.'

She pulled the girl to the entrance. 'I'd say you'll need two or three stitches. St Mary's Hospital is two blocks that way.' She pointed. 'Go to the emergency room. Tell them you had an accident. You slipped, cut your cheek, tore your skirt.'

'Will they believe me?'

'It doesn't matter. It's your business.' The woman shrugged. 'Unless you want to go to the police.'

'Good God, no!' the girl replied, a kind of agony there. 'That's the last thing I want.'

The woman stepped out, picked up the fallen umbrella and gave it to her. 'Then go, my dear, and don't look back. It didn't happen, none of it.' She stepped back and picked up the girl's purse where it had fallen. 'Don't forget this.'

The girl took it. 'And I won't forget you.'

The woman smiled. 'On the whole, I'd rather you did.'

The girl managed a small smile. 'I see what you mean.'

She turned and hurried off, clutching the umbrella. The woman watched her go, examined the bullet hole in her hat, put it on, then opened her own umbrella and walked away in the opposite direction.

Two blocks north, she found the Lincoln parked at the kerb. The man behind the wheel was out and waiting for her as she approached, a large black man wearing a grey chauffeur's suit.

'You okay?' he asked.

'I'm here, aren't I?'

She got into the front passenger seat. He closed the door, went round and got behind the wheel. She strapped herself in and tapped his shoulder. 'Where's that flask of yours, Hedley, the Bushmills whiskey?'

He took a silver flask from the glove compartment, unscrewed the cap and passed it to her. She swallowed once, twice, then handed it back.

'Wonderful.'

She took out a silver case, selected a cigarette and lit it with the car lighter, then blew out a long stream of smoke. 'All the bad habits are so pleasurable.'

'You shouldn't be doing that. It's not good for you.'

'Does it matter?'

'Don't say that.' He was upset. 'Did you get the bastard?'