Clare Keightley was cleaning the smoke damage from the spectrograph in the laboratory when the Doctor knocked on the door and entered.
‘Hello,’ he said. ‘I'm looking for Chris Parsons.’
Clare smiled apologetically. ‘You've just missed him, I'm afraid.’
The Doctor suddenly spied the book, lying on a bench. ‘A-ha!’ he exclaimed triumphantly.
‘Can I give him a message?’ Clare suggested helpfully.
The Doctor gingerly picked up the book. ‘This isn't yours?’ he asked.
‘No,’ replied Clare. ‘Is it yours?’
‘No. It belongs to some friends of mine.’
‘Strange book,’ Clare observed.
‘Strange friends,’ replied the Doctor, ‘and careless; strangely careless... Why did you take it?
‘I didn't,’ replied Clare defensively.
‘Look, what is all this about?’
The Doctor looked up from examining the book. ‘What's what about?’
‘Have you read it?’
‘Hardly,’ said Clare. ‘The writing looks more like an explosion in a spaghetti tree.’
The Doctor was taken aback at this simile. ‘Like what?’
‘Where did it come from? What's it made of? Why did it make the spectrograph blow up?’
His eyes widened in surprise. ‘It did that?’
Clare nodded. ‘Yes.’
The Doctor stared at the book and then at Clare. Suddenly he broke into a large, toothy grin. ‘Hello, I'm the Doctor,’ he said, extending his hand. ‘You're...?’
‘Clare,’ she replied, accepting his handshake, ‘Clare Keightley.’
‘Can I have a look at your spectrograph?’ the Doctor asked.
Professor Chronotis had been right about the kitchen being a long way from the console room. It had taken Romana a long time to get to the kitchen and back. She entered the TARDIS console room, carrying a full bottle of milk, and went to the console. She was about to open the doors, when she hesitated, and changed her mind.
‘K9?’ she called.
The Doctor's robot dog glided around the console towards her. ‘Mistress?’
‘Do you want to come out and be useful? This doesn't seem to be just a social visit after all.’
‘Affirmative, Mistress,’ replied K9. ‘My function is to assist you.’
‘Well you can tell me how old this milk is for a start.’ She bent down and held out the bottle.
K9 extended his probe and scanned the bottle. ‘It has been in the stasis preserver for only thirty years. It is perfectly fresh.’
Romana nodded, and straightened up. ‘Good.’ She operated the door control. ‘Come on, I'll introduce you to the Professor.’
The room was in a much worse state than before; many of the Professor's books had been scattered around the floor. The motionless form of the Professor lay where he had fallen.
Romana did not immediately register this scene as she left the TARDIS. ‘I've got the milk!’ she called holding the door open for her robot dog to follow her out of the police box. ‘Come on, K9.’ She shut the door behind him, and turned to take in the scene before her.
‘Professor!’ Romana immediately noticed his death-like state. She hurried over and bent down to examine him, depositing the now-forgotten bottle of milk on the tea table.
At that moment, there was a knock at the door, and she looked up in alarm. ‘Who is it?’ she demanded anxiously, fearing the worst.
The door opened, and Chris Parsons entered. ‘Ah, it's me, Professor,’ he called as he came through the door. ‘I just came back to...’ He halted as he saw Romana bent over the Professor's prone form. ‘What's happened?’ he gasped when his voice returned. ‘Is he all right?’
‘I don't know,’ Romana replied tersely. ‘I think he's dead.’
K9 completed a scan of the Professor's body. ‘Negative Mistress,’ he reported. ‘He is alive but he is in a deep coma.
‘Well what's happened to him?’ demanded Chris, failing to take in for the moment the absurd notion of a talking robot dog.
‘Processing data,’ reported K9.
‘Do you know him?’ Romana asked Chris.
Chris shrugged apologetically. ‘Hardly at all. He just lent me a book.’
‘A book!’ exclaimed Romana. ‘We've been looking for a book! Are you whatsisname, Christopher Parsons?’
‘Chris Parsons, well, yes,’ he confirmed.
‘Have you got it?’ she inquired. ‘The book?’
Chris shook his head. ‘No. I left it back at the lab. You see, I couldn't understand...’
Something else occurred to Romana. ‘Isn't the Doctor with you?’
‘Well how would I know?’ replied Chris indignantly. ‘I didn't know the Professor was ill!’
‘No,’ explained Romana patiently, ‘The Doctor.’
Chris looked puzzled. ‘What?’
‘Mistress,’ K9 chipped in. ‘The Professor has been subjected to psychoactive extraction.’
‘Will he be all right?’
‘Physical prognosis fair. Psycho prognosis uncertain.’
Chris finally focused on K9. ‘It's a robot,’ he stated in sudden wonderment.
‘Of course,’ replied Romana, her attention on the Professor.
‘A robot dog.’
‘Yes,’ Romana smiled slightly at his astonishment.
Romana's smile vanished, slightly put out by the fact that Chris had accepted K9 so readily. She turned her attention back to the matter of the Professor. ‘K9, you said psychoactive extraction?’
‘Affirmative Mistress,’ confirmed K9. ‘Someone has stolen part of his mind.’
Chris frowned. ‘What did your dog say?’
‘Someone has stolen part of his mind,’ K9 repeated. ‘His attempts to resist have caused severe cerebral trauma. He is weakening fast.’
Reality began to assert itself on Chris' mind. ‘Is all this for real?’ he asked weakly.
Romana ignored the question. ‘Do you want to make yourself useful?’ she inquired, fixing him with a critical look.
‘Well, if I can,’ he said dubiously, already feeling out of his depth.
‘Go and get the medical kit from the TARDIS,’ she instructed.
Chris' mouth sagged open. ‘From the what...?’
Romana pointed at the TARDIS. ‘Over there. Go in, first door on the left, down the corridor, second door on the right, down the corridor, third door on the left, down the corridor, fourth door on the right...’ She hesitated, mentally checking her directions.
‘Down the corridor?’ prompted Chris hopefully.
‘No,’ she replied decisively. ‘White cupboard opposite the door, metal case, top shelf.’
Chris boggled. ‘For a minute I thought you were pointing at the police box,’ he admitted.
‘Please get it,’ Romana urged.
Shaking his head, Chris went over to the TARDIS, pushed open the door and stepped in. Moments later, he stepped out again. His mouth worked up and down but no words came out as his brain struggled to cope with what he'd just witnessed.
‘Hurry up!’ Romana insisted, and Chris re-entered the box, somewhat numbly. Romana turned her attention back to the Professor. ‘Professor? Can you hear me? Professor?’
‘Mistress,’ reported K9. ‘His mind has gone.’
‘But you just said part of it, K9.’
‘Affirmative. The part that is left is totally inert.’
‘Professor!’ repeated Romana desperately.
‘No response, Mistress,’ reported K9.
At this point, Chris re-emerged from the TARDIS, panting from having run the whole way there and back. ‘How do you... have you got a patent for that thing?’ he gasped.
‘Have you got the kit?’ inquired Romana.
Chris produced a white metal case. ‘Here.’ He brought it over and placed it on the floor beside the Professor.
‘Thank you,’ said Romana gratefully. She opened the case and took out a half-circle - shaped band of metal, centered with a raised disc. She placed it over the Professor's neck like a collar.
‘What are you doing to him?’ Chris asked.
Romana activated the device. Flashing lights appeared on the disc and along the length of the band. ‘He's breathing and his hearts are beating so his autonomic brain is still functioning,’ she explained. ‘This collar will take over those functions and leave his autonomic brain free.’
‘What good will that do?’
‘He should be able to think with it,’ Romana replied.
Chris snorted in disbelief. ‘Think with his autonomic brain? The human brain doesn't work like that. The different functions are separated...’
‘The Professor isn't human,’ she told him.
The Doctor was examining the damaged spectrograph, watched by Clare.
‘The book must have stored up vast amounts of sub atomic energy and suddenly released them when the machine was activated,’ the Doctor hypothesised. ‘Does anything strike you about that?’
Clare was confused. ‘What?’
‘It's a very odd way for a book to behave.’ He abandoned the spectrograph, and picked up the book.
‘I would have thought that was obvious,’ Clare retorted.
The Doctor looked up from the book. ‘Never underestimate the obvious,’ he advised.
‘But what does that tell us?’
‘Nothing,’ replied the Doctor. ‘Obviously.’
‘So obviously it was meant to tell us nothing, which is exactly the opposite function of a book. Therefore it isn't a book!’
Clare was about to question the dubious logic behind this reasoning when a printer chattered into life, tucked away in a corner of the lab. She hurried over and tore off the printout. ‘It's the results of a carbon dating test we ran,’ she explained, her eyes scanning the figures on the page. ‘Doctor! This says that it's minus twenty thousand years old! What does that mean?’
The Doctor's features paled. ‘Not only is this book not a book, but time is running backwards over it. I think I'd better return it as soon as possible - don't you?’
The stranger had once more returned to his spacecraft. He stood on the bridge beside a scaled-down version of the hexagonal cone from the Think Tank station. The sphere was perched on the apex of the cone.
‘Playback!’ he ordered.
The holographic screen materialised before him, and the stranger saw himself standing in the Professor's study, from the Professor's perspective. ‘Further back,’ he commanded.
The picture broke up, and reformed as an image of the Doctor and Romana in the Professor's study. The picture was clear apart from the features of the Doctor and Romana, whose forms were heavily distorted. Their faces were completely unrecognisable.
The stranger frowned angrily. ‘Trace memories of the book,’ he instructed.
The picture changed to an image of Chris Parsons in the Professor's study, but again, his features were obscured.
‘He had great mind control,’ the stranger observed with a note of respect in his voice. ‘Find any trace of the book at all.
The picture broke up completely. Fragmentary images faded in and out without definition. Finally, the screen merely displayed static.
‘A brave man,’ the stranger said. ‘The effort will almost certainly prove fatal.’
‘The collar is functioning,’ said Romana. ‘Is there any trace of conscious thought in his mind, K9?’
‘Processing data, Mistress,’ reported K9. ‘Too early to tell. Another few seconds.’
‘Good,’ said Chris.
Romana stared at him. ‘What do you mean, good?’
‘Well don't you see? When you work as a scientist, you don't always know where you're going, or that there is even anywhere to go, that there aren't going to be big doors that stay permanently shut to you. But I look at all this marvellous stuff of yours and I know that a lot of things that seem impossible are possible. So good. I take it that you're...’
‘No, I mean that you're not from Earth?’
‘Mistress,’ interrupted K9. ‘The Professor's condition is rapidly deteriorating.’
‘Isn't there anything we can do?’ Romana asked desperately.
‘Negative, Mistress. The condition is terminal.’
‘But is he thinking?’ she urged. ‘Can he hear us?’
‘Minimal cerebral impulses detectable, Mistress.’
‘Can he talk?’
‘Negative. The speech centres of the brain are inoperative.’
Chris shrugged fatalistically. ‘Well, your collar was a nice idea, but...’
‘Shhh!’ exclaimed Romana. ‘Wait a minute.’ She put her head down on the Professor's chest. ‘K9, can you amplify his heart beat?’
‘Affirmative, Mistress.’ K9 extended his probe to the Professor's chest, and through K9's speakers could be heard the fast, irregular beating of the Professor's hearts.
‘Brilliant!’ exclaimed Romana delightedly.
‘The Professor is a brave and clever man,’ Romana said solemnly. ‘Listen.’
‘I don't understand,’ Chris confessed.
‘He can't talk, but he's interfering with the collar. He's beating his heart in Gallifreyan morse!’ Romana leaned close to the Professor's head. ‘I can hear you, Professor. What do you want to tell us?’
The beats paused briefly, and then started again. Romana listened intently, translating the message aloud. ‘“Beware... The... Sphere... Beware... Skagra... Beware... Shada... The... Secret... Is... In... The...”’
The beats suddenly stopped.
‘He is dying, Mistress,’ K9 reported.
‘All life function has now ceased, Mistress. The Professor is dead.’
Romana buried her face in her hands.
The Doctor rode back through Cambridge on his borrowed bicycle, the book safe in the bicycle's carrier basket. Crossing a single-lane footbridge across the river Cam, the Doctor was forced to come to a halt by a tall man standing in the middle of the bridge. The Doctor warily eyed a large silver sphere balanced in the stranger's hand.
‘Doctor,’ said the stranger.
‘Yes,’ replied the Doctor hesitantly. ‘Who are you?’
‘I am Skagra. I am the one who wants the book.’
The Doctor made an effort to cover the book in the carrier basket with the end of his scarf. ‘Ah, well, I'm the Doctor, and you can't have it I'm afraid. I've hidden it.’
‘Hidden it?’ echoed Skagra, mockingly. ‘You attempt to hide it from me?’
‘Yes. It will be taken to a place of safety.’
‘Oh, just a little place I have in mind,’ smiled the Doctor.
‘Doctor,’ said Skagra calmly. ‘You will give to me everything that you have in your mind... Your mind shall be mine!’
The Doctor considered this for a moment, and then replied. ‘I'm not mad about your tailor,’ he remarked, eyeing Skagra's ‘borrowed’ clothes.
The sphere rose from Skagra's hand, and floated unhurriedly towards the Doctor. The Doctor backed away, but the sphere continued towards him. He paused, and the sphere came closer, targeting in on his forehead.
At the last possible moment, the Doctor ducked, and pushed forward at the same time. The sphere travelled over the Doctor's head and the Time Lord's feet engaged the bicycle pedals. Before the sphere could change direction, the Doctor was cycling off across the bridge, knocking Skagra aside.
Hovering for a moment to gain its bearings, the sphere then shot off in hot pursuit. Skagra smiled, certain that the sphere would find its target, sooner or later. Unlike the Doctor, the sphere would not tire.
Ringing his bell at every corner to warn pedestrians and fellow cyclists, the Doctor rocketed through the back streets of Cambridge, relentlessly pursued by the sphere.
‘“You leave the Pennsylvania Station ‘bout a quarter to four / Read a magazine and then you're in Baltimore / Dinner in the diner, nothing could be finer / Than to have your ham and eggs in Carolina...”’ A group of students were singing under a lamppost as the Doctor sped by, closely pursued by the sphere. The choristers were so involved in their singing that they failed to notice either the Doctor or the strange sight of the floating sphere. ‘“Chattanooga Choo-Choo, won't you choo-choo me home...”’
As the strains of their song receded into the distance, the Doctor swerved into a small side street, hoping to lose his pursuer, but with little success. At the next turn, he tried the same tactic again, swerving wildly across the lane and down an alleyway. To his horror, the book slipped from the basket, and fell to the ground. He glanced over his shoulder, hoping to have time to go back and retrieve it, but the sphere was almost upon him. Redoubling his efforts, he cycled away.
Moments later, Skagra entered the lane, guided by a mental empathy with the sphere. Spying the book, he bent and picked it up, smiling triumphantly. The prize was his; the Doctor's mind would be a bonus.
Emerging on to a street crowded with pedestrians, the Doctor abandoned the bicycle, resting it against a signpost that read “NO CYCLING”. ‘I beg your pardon,’ he said to the sign, and then ran off through the crowds. The sphere homed in on the bicycle, and knocked it over before reorienting itself to the fleeing form of the Doctor and setting off in fresh pursuit. A throng of startled students parted obligingly for the hovering sphere.
The Doctor had entered a short alleyway, bordered on both sides by high brick walls. One by one, he tried each of the doors along the alleyway, but they were all firmly locked. Preparing to retrace his steps, he turned and saw the sphere enter the alley and start towards him.
In desperation, the Doctor turned his attention to the end of the alley, blocked by a tall wire mesh gate, padlocked shut. He checked the lock and rattled the gate, but to no avail. He then tried scaling the mesh, but it was too fine to allow him a foothold. The sphere was very close as the Doctor dropped to the ground. He attempted to wriggle through the very narrow gap between the bottom of the gate and the road. He got his legs through, but then became stuck. Looking up in desperation, he saw to his alarm that the sphere was hovering close to his forehead.
The Doctor could hear the babbling of many overlapping voices as the sphere moved in to claim his mind...