Jack walked slowly across the Plass, Tosh and Gwen following. He coughed, painfully aware of his weakness, the virus once again taking hold, and fretted that it was preventing him doing what was needed.

They had been out all night, scouring the streets looking for Ianto. They had quickly located his car on Coglan Street, outside an empty warehouse, but there was no sign of his presence there or anywhere else. His gun had been dropped on the ground outside the Hub doors, and his phone was left in his car. He had seemingly vanished off the face of the earth.

Jack didn't for a moment believe Ianto was willingly involved in what was happening, and he knew of many techniques that would be able to coerce his cooperation, most of them not very pleasant. What was frightening him most of all was that, assuming the attack on him was the objective, Ianto was surely now expendable, and was quite possibly dead. He pushed the thought away. He didn't want to think about it.

"Jack, we can keep looking," said Gwen anxiously from behind him. "You need to be resting, and let Owen and Martha help you."

He stopped, and turned slowly. It was an effort to frame his thoughts into communication. He never usually got tired like this, and he figured wryly that he would be a lot more sympathetic when the others got worn out in future. "I don't know where to look," he admitted. "Don't know what else to do." He coughed. "He wouldn't do this."

They each took an arm. "We know," reassured Tosh. "We'll keep looking. Come on." They guided him towards the Tourist Office entrance. He thought fleetingly there was a comment about having a beautiful lady on each arm that was going begging, but he couldn't quite put the thought together and soon gave up the attempt.

As they handed him over to Owen, Jack said, "Go home. Get some rest." He forestalled their objections. "We have no leads. It's alright."

Back in the med unit, he watched listlessly as Owen moved around, checking equipment. "Torchwood budget should spring for a nurse," Owen complained. "This isn't really my thing."

He's scared, Jack thought. They all are. Make an effort, Jack. He smirked. "Really? You do it so well." He leaned back against the pillows. "I am getting so tired of this room. We should redecorate."

"That's definitely not my thing," retorted Owen. He hesitated. "Jack, have you been sick before? I mean, since …"

"Oh yeah," said Jack. "Several times. Dengi fever was a bitch."

Owen raised an eyebrow. "You scare me, Harkness."

Jack chuckled, then coughed. "Where's Martha?"

"Sick of my company already?" enquired Owen.

"Martha's better looking," grinned Jack.

"No arguments there. She's at her hotel, getting some rest."

"Have you slept?"

"Mmm," said Owen evasively.

"Owen," said Jack authoritatively. "Get some rest."

Owen finally nodded reluctantly. "I'll lie down on the couch for a bit." He paused. "Look, I know you don't need reassuring from me, but for what it's worth, teaboy might be a bit neurotic, but he'd die for you. He's not involved in this, not by choice."

"Thank you," said Jack. He shut his eyes, and tried not to think about Ianto dead or dying somewhere.

Two days later, Martha and Owen were sitting in the lab in silence. Owen broke the silence first. "You've got to do it."

"I know," she replied. "Jack's not going to like us bothering him."

Owen shrugged. "We're doctors. We're requesting a … specialist consult in the best interest of our patients." He paused. "Don't you think he'd want to be told?"

"You're right," said Martha, picking up the phone and dialling. "Voicemail," she sighed, "naturally." She waited, and then spoke. "Doctor, it's Martha. Jack needs you. Please come to Cardiff as soon as you can." She hung up.

Owen frowned. "Shouldn't you have explained the problem?"

"No need," she said. "He'll come."

"But when?" retorted Owen. "If he's off saving somebody or other …"

The sound of the TARDIS filled the air. Martha grinned. "Time machine, remember?"

They headed out into the main area of the Hub. "Did you call him?" asked Gwen.

"We had to," said Owen, as the TARDIS door opened.

"Hello," said the Doctor cheerily. "Martha called?" He caught sight of her. "Why are you limping?"

"It doesn't matter," said Martha. "Oh, I'm so glad to see you." She hugged him.

He returned the embrace, as he considered the tired and worried faces around him. "I think you'd better tell me what's wrong."

Jack opened his eyes to Martha's touch. "Hey," he whispered. "I was dreaming. Thought I heard the TAR …" He broke off as he saw the Doctor. "Doc? What … oh, did they call you?"

"Yes they called me," said the Doctor, "and quite right too." He laid a hand on Jack's forehead, assessing his temperature with a touch. "How are you, Jack?"

"Been better," admitted Jack, and coughed. "Apparently someone's out to get me."

"Angry spouse?" suggested the Doctor.

Jack smiled. "Funny." He gulped in some air. "Doc … Ianto …"

"I know," said the Doctor. "I don't want you to worry. Right now, you need to sleep." He touched fingers to each side of Jack's forehead, and his eyes immediately closed. The Doctor straightened up and turned to the others, deadly serious. "Let's see this virus."

In the lab Owen called up a three dimensional representation of the virus on a computer screen, and the Doctor examined it with interest. He whistled. "That is a beautiful piece of work."

"That beautiful piece of work is killing Jack over and over," Martha reminded him.

"Yes," said the Doctor. "If you wanted to kill someone who couldn't be killed, you might have to settle for the next best thing. So who wants to kill Jack?"

"Umm … lots of people," said Owen.

"With the technology and expertise to make that?" The Doctor tapped the screen. "That's not from this time or place."

"Can you help?" said Martha.

"I hope so," said the Doctor. "But first … do you have any more of the blood you took from Ianto?"

Owen and Martha looked at each other, puzzled. "Yes," said Owen.

"Good," said the Doctor. "Back in a bit." He headed for the TARDIS.

"I've got some news for you," said the Doctor in the med unit, much later.

Jack's temperature was rising, and his face was damp with sweat. "News," he whispered. "Mm?"

"I've been looking at Ianto's blood sample, and I found something." He recited a long complicated chemical formula.

"I would have thought it couldn't exist if I hadn't seen it," Owen commented. "So we weren't even looking for it."

"And we had no idea what it was, of course," added Martha.

Jack was looking at the Doctor, confused. He pulled the oxygen mask off. "Program … how…?"

The Doctor gently replaced the mask. "I'll find out, I promise."

"Program?" queried Martha.

"What it says," said the Doctor. "You inject someone with that, and you can make them do whatever you want. Essentially you can program them like a computer, and they cannot resist."

"To shoot people and infect them with a deadly virus?" said Martha.

The Doctor nodded, and looked at Jack. "I know you hadn't stopped believing in him, but I thought you'd want to know."

"Thank you," whispered Jack.

"Where does this 'Program' come from?" asked Owen as they returned to the lab.

"At least five centuries in the future." He looked at both of them. "Go home. Get some rest. I'll keep an eye on him."

He persuaded them to leave finally, and sat down in the lab, staring at the virus still displayed on the screen. He was starting to have a very uneasy feeling about who was involved. The virus had to have been created by a brilliant scientist with expertise and access to future technology, access to Jack's DNA, knowledge of Jack's unique condition, and a reason to hate him. That narrowed the list considerably. Add to that the use to which Ianto had been put, which was purely malicious, and it was virtually confirmed as far as the Doctor could see. The Master was back. Again. And what has he done with Ianto? the Doctor wondered. Why does he want him? That was one thing he couldn't understand.