The Doctor and Jo Grant had been doing a lot of catching up. Since landing on the planet Spiridon they had been having their separate adventures along with the group of Thals trying to disrupt the plans of the Daleks. Now, with night approaching, they had just about caught up.

"...Then I changed the setting on the last bomb, grabbed the other two and just ran. That's when I met up with your group."

"Well, Jo, you have been busy, I must say. You must be exhausted."

"Actually, Doctor, I'm not. It must be the adrenaline."

The Doctor nodded. "You could well be right, Jo. But it's going to be a long day tomorrow, you should get some rest."

Jo shook her head. "I'm fine, honestly. Why don't you sleep for a while?"

The Doctor smiled at his companions concern. "You know I don't need as much sleep as a human and I had a lot of time to rest in the TARDIS."

"I thought you were dead," Jo confessed.

"It would take a lot more than that to kill me," the Doctor told her.

Jo seemed reassured. Then another thought occurred to her.

"Doctor, you never told me the story behind your becoming a noble of Draconia."

"Well, that is rather a long story."

"We have all night," Jo reminded him.

The Doctor grinned at her. "Very well, but I'll condense it where I can. It all started like this..."

***

The peace and quiet of the Imperial Palace was noisily disrupted by the intrusion of a tall blue box with a light flashing on top, which materialised with a grating, roaring sound in a side corridor. A minute or two passed before one of the doors opened and two men emerged.

"Is there any point in me asking where we are, Doctor?" the younger man said.

His companion, an elderly man with shoulder length white hair, looked around him with genuine interest. He barely noticed his companions comment.

"Hmm?" said the man addressed as the Doctor. The younger man sighed.

"Do you know where we are?" he asked again, with exaggerated patience.

"Well, it's certainly somewhere very grand," the Doctor replied, taking in the ornamentation, the plush carpeting and the artwork on the walls and ceiling. "Yes, somewhere very grand indeed, Steven."

Steven was used to the Doctor's vagueness by now, after travelling with the mysterious old man for some time. It didn't mean he liked it though.

"It would be nice to know what planet we are on," he commented.

"The only way to find out is to explore," the Doctor told him, somewhat tetchily. "You should know that."

"Yes, Doctor," Steven replied meekly. Since he had been travelling alone with the Doctor he had found it was sometimes best to keep the peace.

The Doctor was already exploring, examining a tapestry closely. He turned and gestured for Steven to see what he had found.

The young man looked where the Doctor indicated. He saw a hunting scene, the participants being humanoid but with reptilian features, carrying spears.

"Alright," said Steven, "we're not on an Earth colony. But it doesn't tell us where we are."

The Doctor smiled. It was the one Steven thought of as his self-satisfied smirk.

"Given the features of the people in the tapestry, I would conclude that we are somewhere in the Draconian Empire. Maybe even on Draconia itself."

Steven thought for a moment. "I've heard of them," he said, "but in my time the human race have not met them yet."

"Well, young man, it looks like you could be the first."

As if to prove the Doctor right the sound of running feet sounded down the corridor. Within seconds the Doctor and Steven were surrounded by beings like those shown on the wall hanging. These, however, had energy weapons.

"You have violated the Supreme Palace of the Emperor of all Draconia," said the Draconian in charge. "You will be executed where you stand!"

***

Jo gasped in surprise, then relaxed a little. "Well, they obviously didn't execute you. So, what happened?"

The Doctor smiled. "A couple of pieces of good fortune, well, for Steven and myself, anyway. Just as the guards raised their weapons..."

***

Just as the guards raised their weapons to carry out the order, another voice sounded in the corridor.

"Stop! What is going on here?"

The Draconian in charge bowed low before the newcomer. "Your Highness, we discovered these, humans, lurking in this corridor. They obviously plan to murder the Emperor and all the Royal household, your good self included."

"Do they indeed? You," he pointed a long finger at the Doctor, "does Guard Captain Slarn speak the truth?"

The Doctor drew himself up to his full height and grasped the lapels of his frock coat. "No, sir, he does not."

There was a murmured hiss of disagreement from the guards. The newcomer regarded the Doctor with what could be considered amusement.

"And what is your version of events here?" he asked.

"Myself and my friend here are travellers. We arrived here by accident. We were trying to get our bearings when we were descended upon by these ruffians, your Highness."

This caused more muttering among the guards, which turned to cries of alarm as Guard Captain Slarn collapsed.

The Doctor was at his side in an instant, feeling for a pulse and loosening his collar. The guards started to surge forward.

"Halt!" called the newcomer.

"But they bring the Great Plague into the Royal Palace," said one of the men. "They should be killed now."

"Would you defy your Prince Regent?"

The guard looked abashed. "No, my Prince, I would not."

The Prince knelt down beside the Doctor, who was just finishing his examination. Slarn's green face was covered in red blotches.

"He has been struck down by some kind of virus," the Doctor concluded. "Did I hear one of your men say something about a 'Great Plague'?"

"Yes," the Prince replied. "About three weeks ago, an unknown disease started spreading among the local villages. Within a week it was rife in the city. Already more than three thousand Draconian citizens are dead, with twice that number infected."

The Doctor stood up, his face grim. "If I am to be of any help to you in combating this disease, I will need a laboratory, tissue samples, both from living victims and from the dead, and access to medical files on your people."

The Prince looked suspicious. "Why should I trust you? You appeared from nowhere and it was only my curiosity that saved you from being shot."

The Doctor beamed at him. "Look at it this way, young man. What have you got to lose?"

The Prince sighed. "I'll get your laboratory sorted out straight away."

"Splendid," the Doctor replied, clapping his hands together.

"But be warned. If you have no results in two days, I'll let the guards execute you both!"

***

A couple of hours later the Doctor surveyed his surroundings with obvious approval.

"Yes, yes, this will do nicely. Yes, very nicely indeed."

Steven was looking around the laboratory himself. It seemed well equipped, though he was only a starship pilot, not a scientist. He couldn't help thinking, however, of the time limit imposed on them.

"Don't forget, Doctor, we have less than two days."

The Doctor's face turned serious. "Yes, my boy, yes. We must start at once."

***

"Well, you must have found a cure or we wouldn't be sat here talking," Jo commented. "How did you manage it?"

"It was a bit of a coincidence, really. I was talking to one of their doctors, a chap called Margle..."

***

"Margle, I was wondering, did anything else strange happen around the time this plague started, hmm?"

"Not that I can think of," the Draconian replied. He had been a great help to the Doctor in his study of Draconian biology. He didn't seem much for court gossip,though.

"Why do you ask, Doctor?" Steven inquired. He was feeling pretty useless, as all he seemed able to do to help was fetch and carry for the Doctor.

"Because I don't think this disease is natural to Draconia. It's protein structure appears to be alien to this planet."

"Of course!" exclaimed Margle. The Doctor and Steven looked on expectantly. "The defence satellites shot down an unmanned probe of some kind just over three weeks ago, days before the first case was reported."

"What became of this probe?" asked the Doctor.

"I believe it landed, virtually intact, about twenty miles from here."

"And the first village that reported symptoms?"

"Is very close to the landing site," confirmed Margle.

"Didn't anybody make this connection before?" Steven asked.

The Draconian shook his head. "All our efforts were taken up with fighting the disease, not with looking for a cause."

"You should always look for a cause, Margle," the Doctor told him. "Only then can you hope to understand anything."

"You are very wise, Doctor."

The Doctor smiled. "Nonsense, young man. Now, what became of this probe?"

"It is stored at the Ministry of Science, just across the square."

At that moment the Prince arrived.

"You're just in time," the Doctor told him. "I need Steven here to go to the Ministry of Science for me. Can you get him a pass, hmm?"

The Prince ignored the Doctor's question. "I come with bad news. The Emperor has contracted the disease. I need results, Doctor, and I need them now!"

The Doctor squared up to the Prince. "Then it is imperative that you co-operate with me as much as possible."

For a moment the Prince looked ready to argue. Then he sighed. He nodded to Steven. "Come with me," he said, "we can go to the Ministry together." They headed for the exit, then the Prince turned back to the Doctor. "I'm not ready to become the sixteenth Emperor just yet. You must succeed."

"I'll do all I can," the Doctor replied.

***

"So, did the Prince have to become the new Emperor?" Jo asked.

"Well, not this time. Thanks to the information brought back by the Prince and Steven..."

***

The Prince and Steven were back within the hour, reporting their findings to the Doctor.

"As Margle told us, it's mostly intact. The power source seems to have taken some damage."

"What kind of power source?" the Doctor inquired.

"Some kind of fusion generator, but of a design I'm unfamiliar with."

The Doctor tapped his forefingers to his lips and started pacing the room. Steven suddenly realised how hot he felt.

"You say you didn't recognize the type?" the Doctor asked.

"Yes, I..." Steven trailed off, suddenly feeling dizzy. "I don't think..." He collapsed, much as Slarn had done the day before.

The Doctor checked him over quickly. Red blotches were already coming through his skin. "Yes, it's as I thought."

"Does he have the disease?" asked the Prince.

"Yes," the Doctor replied, "but he's also given me the cure."

***

Steven sat up in bed. He could not remember getting into bed, but here he was. In fact, he could not remember much at all.

"How are you feeling?" asked a familiar voice.

"Like I've been worked over by Daleks," he replied.

"Good," the Doctor said. "You're on the mend."

"What happened?"

"You gave me the clue to solving this plague business."

"I did?"

"Yes, my boy. It was radiation poisoning caused by the unshielded fusion system of that probe. I mixed up an anti-radiation treatment from some local herbs and a few special ingredients from the Ship."

"So, we're not about to be executed?"

"Quite the reverse. The Emperor wants to honour us."

***

The throne room was full of Draconians, as Steven supposed it should be. On the throne itself sat the Emperor, flanked by two guards. One of the guards, Steven was pleased to see, was Slarn.

As coached by the Prince, the Doctor approached the Emperor, bowed low and placed his forehead on the ring on the Emperor's right hand.

"My life at your command, sire," he intoned. He then stepped down and let Steven take his place.

"There will always be a place for the two of you among the nobles of Draconia," the Emperor told them. Repeating the ritual words again, the Doctor and Steven bowed once more and left the throne room.

***

"And then we left Draconia, bound for another adventure," the Doctor concluded.

"Lucky for us you cured the Emperor, or we could be sitting in a Draconian dungeon while the Daleks take over the galaxy."

"Yes, well, we haven't beaten the Daleks yet. That's a job for morning. Why don't you get some rest now?"

Jo yawned. "I think I will. I'm suddenly quite sleepy."

The Doctor nodded. "My stories tend to do that to people. Goodnight Jo."

But Jo had already fallen asleep.