A few days later, John asked Mary to look at another experiment. He took her into a long, quiet room at the back of the factory. The room was full of the noises of small animals.

'So what do you want to show me?'she asked.

'I've been testing the waste products,' he said. 'Here, look at this.' He gave her a sheet of paper. 'Some of these rats have had the waste products in their food and drinking water. There's no real problem yet. One or two have become ill, but not many. There's nothing very serious.'

Mary read the results carefully. She didn't like this kind of experiment, but she knew it was necessary. And John was right; no rats had died, and not very many were ill.

'This,' he said. He opened a box by the window. 'These ten rats have had the waste products in their drinking water for two weeks now. I gave them a lot-five parts per million. They're going to have babies today. If the babies are OK, we've got nothing to worry about.'

'I know, I know,' he said. But he wasn't listening. 'Look,' he said excitedly. 'Some of them have been born al-ready!'

'Oh, John,' she said. 'What an awful thing to do!'

He lifted some of the baby rats out of the box and looked at them through a magnifying glass.

He looked at her strangely. 'It's awful, isn't it? But I had to know. And remember, Mary-their mothers have had five parts per million of these chemicals in their drinking water for two weeks. That's a lot-much, much more than we're putting in the river.'

Mary looked through the magnifying glass. She began to feel ill. There was a long silence.

'Of course, of course.' John put his hand on her arm, to comfort her. But it was the same hand-the hand that had held the rats. 'Of course we'll stop it, if we need to, Mary. The company can build machines to clean the waste products. I'll start my report for David Wilson next week.'

'Oh dear,'he said at last, sadly. Perhaps there is a prob-lem. Look!'

Mary looked away from the rats. She remembered the beau-tiful afternoon that they had spent with John's children, sail-ing on the clear blue water. 'John, these waste products are dangerous!' she said. 'We've got to stop putting them in the river!'

'There certainly is a problem!'mary's voice sounded loud and high in the quiet room. She stared at the small animals under the magnifying glass. 'Baby rats with no eyes, no ears, six leqs! Oh John! John! What have you done?'

'But…' she turned round to face him. His hand fell from her arm. 'Don't you think we should stop making the paint now, John? Perhaps it'll take years to build those machines, and we're putting the chemicals into the river right now!'

A shadow crossed his face. His eyes looked at hers, then away, out of the window.

She remembered her long years of work, the hundreds of unsuccessful experiments. She touched his hand, and smiled. 'I hope so, John,' she said. 'I really hope so.'

She turned, and went quickly out of the room.

'I… don't think we need to do that now, Mary. We're putting very little into the river at the moment. And the com-pany will build those machines, won't they?'