He paused. Ahead of him, he caught sight of a square intersection of two tunnels.

Three ways: which one to follow?

He eased himself back to the previous grille and, by the light filtering through the mesh, examined the piece of paper Barclay had given him. Again he moved forward checking the stencilled numbers over the intersections. FIVE, SIX, SEVEN. Number five was the one to follow. He turned awkwardly and dragged his body at right-angles into the new tunnel. His face and singlet were wet with sweat. In spite of the warm breeze which was blowing along the shaft, and the short distance he had travelled, his arms and legs were beginning to ache intolerably...

Ahead he saw three grilles set close together-as described by Barclay.

Cautiously, he put his eye to the thick mesh, looked through-and sighed with relief. The rocket silo! He had arrived exactly where Barclay had indicated on the sketch plan.

Looking down into the room, Ben could see that he had reached a grille set over the gallery. He looked across, and froze! An engineer with a clipboard was working almost directly opposite!

His hand felt for the four flynuts that held the grille in position, and started to loosen them. The hum of the powerful dynamos would prevent his activities being heard; he was also invisible through the grille-until, that is, it was removed. But where on earth was Dr Barclay?

He removed the top right hand flynut, the left, then began to loosen the lower ones.

The grille began to sag outwards. One touch, and it would fall through-leaving the way clear. He looked across at the engineer to see if he had noticed anything, then saw that the man was looking down and nodding to somebody below.

By pushing his cheek against the warm metal top of the shaft, Ben could just make out, the floor of the silo room and the now empty bomb cradle. The bomb had been loaded into a hatch leading directly into the rocket launching tube and the waiting Demeter Demeter rocket. rocket.

He saw an engineer fasten the large bolt arrangement that closed the square safe-like door of the hatch. Beside him stood Dr Barclay.

As Ben watched, almost holding his breath, he saw Barclay lead the man away, then look up and beckon to the engineer opposite Ben.

After what seemed an age, during which time Ben's neck was horribly cramped by the awkward angle at which he had to hold his head, he saw the engineer climb slowly down the metal ladder, and follow Barclay and the other man out of the room.

The door closed behind them and, for a few precious minutes, the room was Ben's.

He pushed the grille out with his hand, then, as it clattered down, eased himself through and landed on the narrow gallery. He stretched his cramped muscles in relief, and brought out Barclay's instructions.

Following the directions, he started tracing a line of twisted multi-coloured lead wires through the rocket launching controls. His fingers stopped opposite a panel labelled: PUMP SERVO LEADS.

Bringing out his screwdriver, he began to unscrew the panel...

In the tracking room, Cutler had been watching the ambush of the Cybermen relayed by the TV camera. As the last of the Cybermen climbed back into their s.p.a.cecraft, he raised the stub of his cigar, smiled, and screwed it triumphantly into the ashtray. He turned to the R/T technician.

'Tell them they did a great job. Have the Cyberweapons brought down to the guard room.'

He stretched himself, easing his muscles after the tension of the last few minutes.

'Barclay,' he called. He looked around-but the tall Australian physicist was nowhere to be seen.

'Dyson,' he snapped, 'where is Dr Barclay?'

'I don't know, sir-he wasn't here when I got back.'

'Where could he have gone at this time? He's needed right here!'

Dyson, busy with his own calculations, looked up again. 'Er... perhaps he went down to the rocket silo.'

'Rocket silo!' Cutler's face changed, his jaw set. 'We'll see, shall we?' He strode over to the door.

In the long corridor outside the silo, Barclay and the two engineers were in conversation. Outside the sound-proofed room the roar of the mighty dynamos was even louder, and the three men only became aware of Cutler's presence when he was standing beside them.

He pushed the two engineers aside and confronted Barclay. 'Just what are you doing here, Dr Barclay?'

Barclay's jaw dropped. His nervous glance gave him away. 'We were just checking my...'

Without a word, Cutler grasped him by the tunic, thrust him aside, opened the door of the silo room, and rushed in. Immediately, he caught sight of Ben's head inside the panel.

Dropping his hand to his belt, Cutler drew his heavy automatic, and levelled it at the intruder. Taking careful aim, the General's finger tightened on the curved trigger...

As he fired, Barclay pushed his arm aside. The gun boomed, echoing round the metal walls of the silo room-but the bullet missed Ben, struck the metal panel and ricochetted off.

Holding Barclay aside with his other arm, Cutler levelled the automatic at Ben again.

'O.K., sailor,' he ordered, his voice rasping above the hum of the machinery, 'get down here-at the double!'

For a second, Ben hesitated, torn between his uncompleted task, and almost certain death from Cutler's gun.

The rocket had to be stopped-whatever the cost.

He turned back to the exposed wires, but Cutler, in one swift and incredibly agile leap for so large a man, reached the ladder, and grasped Ben's ankle.

Ben gave a cry as he felt himself being pulled backwards. He tried to grab the rail but his head struck the metal platform. He slumped unconscious from the gallery and landed in a heap at the bottom of the ladder.

Barclay saw Cutler raise the gun again. 'Stop!' he yelled. But Cutler replaced it in his holster and turned to the guard who had just entered.

'Get him along to the control room.' He turned to the engineers. 'You two get back on that rocket.'

Cutler turned to Barclay. The man backed away. 'Look, I can explain,' Barclay's voice was shaking.

Cutler glanced at him with contempt. 'Don't bother. You're coming with me right now. I need you. We'll talk about this after the rocket has been fired.'

He turned to the guard who had lifted the unconscious sailor. 'Have his companions brought along, too. Seems I can't rely on anyone else to keep an eye on them.'

'You're treating him like a criminal,' Polly shouted. Ben, his head bleeding, was slumped, still unconscious, in a chair by the main console.

The Doctor was sitting beside him, wide awake but silent. Polly was bathing the back of Ben's b.l.o.o.d.y head.

Cutler turned to her. He had posted guards with drawn carbines on either side of the time travellers. His automatic rested on top of the console. 'As far as I'm concerned, he is a criminal! I'm warning all of you, if that rocket doesn't take off for Mondas, and if my son's life is in jeopardy because of him, I shall take the law into my own hands.' He looked across at Barclay. 'And that goes for you too, Dr Barclay. You'd better do a d.a.m.n good job on this launching-or else!' He turned to the other technicians. 'O.K., start the count down.'

Barclay looked down at the console. 'Preliminary checking is not complete, General. I'll inform all concerned when ready.'

Cutler nodded abstractedly and walked over to the R/T set. He glared at the operator. 'I thought I told you to keep trying to contact Zeus Five Zeus Five? Get with it!'

The R/T technician spoke tremblingly into the microphone. ' Snowcap Snowcap to to Zeus Five Zeus Five, Snowcap Snowcap to to Zeus Five Zeus Five. Come in please.'

After a crackling of static from the loudspeakers, Terry Cutler's voice broke in.

' Zeus Five Zeus Five to to Snowcap Snowcap. Receiving you loud and clear. Over.'

Cutler's dark, heavy-set face lightened suddenly. He leant over, shoved aside the R/T technician, and grabbed the mike. 'h.e.l.lo, son. Any sign of those s.p.a.cecraft in your vicinity?'

'No, sir. I'm all on my lonesome up here.'

'Well watch it, they move mighty fast.'

'Only one question. When are you going to bring me down?'

'We can't do it yet. You'll just have to hold on. We're going to deal with the planet Mondas first. How are things with you?'

'I guess the capsule's getting a little slow at the controls.'

'What about the power?'

'It loses, then picks up again.'

Cutler nodded. 'Yeah, Mondas is affecting it-we'll get you down as soon as we can.'

For the first time the voice of the young astronaut showed a sign of strain : 'Thanks.

Can't be too soon for me!'

Cutler's face looked concerned. 'Good luck, boy-switching off now.'

The astronaut's voice came through almost as an aside. 'Luck ! I'm going to need it.'

As Cutler slowly replaced the mike, Barclay's voice cut in.

'All systems ready to proceed with count down.' His voice echoed through the loudspeakers. 'Barclay speaking. Please check in. Silo Control?'

'Check,' replied the silo engineer.

Polly crouched by Ben. He was coming to; his eyes were half opened-but he seemed dazed. She looked towards the Doctor. 'Doctor, can't we do something?' But the Doctor still seemed half asleep. He shook his head as if lost in a day-dream, and didn't reply.

'Gantry team?' queried Barclay. The answer came: 'A1 O.K.!'

'Fire control?'

'Check! '

'Ben!' Polly said urgently. 'Speak to me, please.'

'Um?' Ben peered round the room, trying to focus. 'Who is that? Who's talking?'

'Keep your voice down,' whispered Polly.

'P... Polly? What happened?'

'Look,' she glanced round the room, 'I'll tell you later.'

Cutler and the team were now too deeply engrossed in the countdown to pay attention to the three time travellers.

'Radar vectors check?' queried Barclay.

'Check,' came the voice. 'T minus one fifty and counting,' said Barclay.

Polly whispered in Ben's ear again. 'Did you manage it?'

Ben held his head in his hands : 'I can't seem to hear you, Poll. My head's splitting apart.'

'Ben, you must remember. Please try and think! Did you manage to do what Dr Barclay told you?'

'I just don't know!'

Suddenly another voice cut in through the loudspeakers. 'Silo here. We have a fault on range computer. Check all circuits.'

'Stop the countdown,' ordered Barclay.

Polly put her mouth close to Ben's ear. 'Does that mean they've found the fault?'

'Dunno,' said Ben, confused.

Suddenly, Cutler became aware of the implication of the last report. He rose from his seat at the console, and pointed the heavy black pistol at Barclay: 'Exactly what is the matter with the range computer?'

Barclay's face went pale. He shook his head. 'Only a minor fault, General.' He spoke into the mike. 'Holding at T minus one and thirty-five.'

Cutler leant forward, his gun pressed against Barclay's chest. 'It'd better be minor.'