He wondered if Susan was back at his bungalow right now. In all probability she was packing her bags and loading them into the Mini. The chances of her turning up at the Centre of the following day were remote.

He glanced in the direction of the telephone, but discarded the idea at once. It wouldn't work. A phone call would not stop Susan from leaving.

Newman felt physically and mentally drained. His thoughts returned to the bats, and the knowledge that he could not risk any interference from Professor Rickers and his students the next day. He had hoped that the creatures would die quickly, but now it looked unlikely. In that case, there was only one solution. He would have to destroy them. They could easily be gassed. The only problem was that the lethal gas was stored in a separate part of the building, under lock and key, and could only be obtained with Haynes's permission, which certainly would not be forthcoming.

He tried to think of alternative means. Perhaps if he filled the glass case with water and drowned the occupants ...

Newman lay down on the sparse couch and stretched himself out. His entire body was crying out for sleep, yet he knew that there was no chance of slumber. His brain was too confused, going over recent events, trying to work out solutions, thinking of Susan, of Fiona, of Haynes and Rickers, and the students. Somehow he did not like the idea of switching off the light and being alone in the darkness with those squeaking, thudding bats. His thinking was becoming illogical, he told himself. They could not possibly get out, but until every one of them was dead there would be no peace in that laboratory.

He lay there just looking up at the plain white ceiling. For the first time in his life he felt totally helpless. Events would control his own actions from now on.

Sometime after the first grey light of dawn had crept in through the uncurtained windows he dropped into a fitful doze. It seemed only seconds since his eyelids had closed before he heard a key being turned in the lock. He sat up with a start. It could only be one of a small group of people who had access to laboratory keys. Haynes, Rickers... Susan!

'Good morning, Professor Newman,' she walked in, closing the door behind her.

Brian Newman was too startled to reply. He simply stared at her in amazement. She was immaculate in every aspect, and there was no evidence of her having spent a troubled night. She barely glanced in his direction, taking off her coat, and then immediately set about her routine duties, sterilising implements, checking charts, and all the time ignoring him totally.

Newman sat up and swung his legs to the floor. His suit was crumpled, his hair awry, and there was a growth of stubble on his chin. He rubbed his bleary eyes, and sighed loudly.

'I could use some coffee,' he spoke softly, a tremor in his voice.

'We have coffee at ten,' Susan Wylie replied formally. 'However, there is coffee, sugar and dried milk in the cupboard if you wish to make yourself a drink.'

He stood up, swaying slightly. His head ached abominably. He looked quickly in the direction of the bat cage. There were still a dozen or so of the creatures flying crazily to and fro, bumping, falling, fluttering up again. No more had died during the night, and that didn't add up. Either the virus was dead, they were immune to it, or else the incubation period in these last few was longer.

'About last night. . . ' he began, clearing his throat.

'I slept well, thank you,' she replied icily without glancing up. 'Now, if you will excuse me, Professor, there are certain items which I must go and collect from the stores....'

'Now listen to me!' he snapped, his level of anger rising fast. Women had cursed him hundreds of times over the years, pleaded with him, cried, but none had ever treated him with indifference.

She ignored him and turned in the direction of the door.

'I said listen to me!' his hand shot out, grasping her by the shoulder and turning her round to face him. 'There are one or two things we've got to get ironed out.'

'I have no idea what you're talking about, professor.' Only her eyes gave away her innermost feelings, bitterness that an outward show of indifference could not cloak.

'You know damned well what I'm talking about!' he rasped. 'About last night at the Shoal Hill Tavern.'

'Oh, so you went drinking, did you?'

'And that wasn't all,' his voice was raised. 'I was with a bird. And I was going to screw her only you stopped me! You put me off my stroke!'

'Me?'

'Yes, you. Out on a snooping trip. Well, I don't blame you, but I can't stand liars.'

'Neither can I, Professor. And just lately you've been telling quite a few yourself.' Her self-control began to snap, and she added savagely, 'You think you're God's gift to women, don't you, Brian Newman? Well, let me tell you this. All you're trying to do is prove something to yourself, though God knows what. Maybe 'conquer and move on' is your motto. Well, I'm not standing for it. You thought you could drive me off, didn't you? That I'd pack and run? Well, I'm not leaving the Centre. 'I'm not giving up a good job because of you. I'll move out of your bungalow so you can have her in the bed all to yourself, but I'm staying right here in this very lab as far as work goes. I'm not going to give you the satisfaction of seeing me go to Haynes and ask for a transfer to Rickers's lab. The pair of you would love that, in your own warped ways, but I'm staying put, bats and all. But lay one finger on me again, try to get familiar with me, and I'll be lodging an official complaint that will really put paid to your career. You've got me with you all the time in an official capacity, and nothing more, whether you like it or not!'

'You bitch!' His left hand went back, and before he could stop himself he had struck her across the face with a resounding slap.

She staggered back, tears filling her eyes, gasping with pain. He stood aghast, mouth opening to voice an apology.

Suddenly everything seemed to explode inside her, and she was hurling herself at him, beating at his body with clenched fists, tearing, scratching, biting, kicking. He staggered back, Susan Wylie clinging on to him, screaming insults at him,

'Damn your he yelled. 'I'll teach you a lesson you won't forget. I'll.. .' His words trailed off as his back met with something solid but movable. The table. He felt the nearside legs being lifted clear of the floor, objects sliding, crashing, splintering, fragments of glass tinkling. In desperation he pushed her away from him, and even as he turned he saw guinea-pigs and other rodents scampering about, frightened, bewildered by their unexpected freedom,

'Oh, God!' he gasped.

Something flew past his face, a rush of air from tiny wings fanning him. Another. And another.

'The bats!' he cried, his face turning a deathly white. 'The bats have escaped!'

Susan Wylie backed away. It was true. The cage of death was lying in splinters, the bats which had died from the mutated virus spilled beneath it. Yet it was the living ones which brought a cry of terror to her lips. They were flying crazily about the room, cannoning into walls, getting up again, jinking, swerving. One hit a row of test-tubes and sent them showering to the floor.

'Under the table!' Brian Newman grabbed her around the waist, dragging her down beneath the long table with him. 'Keep still! They're not after us. It's just that their radars are damaged and they've no sense of direction.'

The high-pitched squeaking was much louder now that the tiny creatures were free of their cage. Newman and Susan heard them striking against the windows. Sooner or later they must find the open one. More breaking glass.

'The window's gone. The big one!' Brian Newman gasped. 'The pane must have been cracked or faulty. They'd never break it otherwise.'