Amy stood, looking at the handsome man stood across the room. She could feel herself heating up a little at the sight of him. Rory saw the obvious blush forming in her pale cheeks and had a bad feeling. The Doctor, completely unaware of what his companions were thinking, stepped forward to greet his old friend.

"What have you got around your neck?" Harkness asked, amused at the bowtie.

"I wear a bowtie now," the Doctor said, proudly fiddling with his bowtie. "Bowties are cool."

"Doctor, who is that?" Amy asked quietly, unable to keep her eyes off the man.

"Amy, Rory," the Doctor began. "This is Captain Jack Harkness. Pheromone personified."

"You can say that again," Amy said, heating up a bit more.

"Who is this lovely young lady?" Harkness asked, stepping towards Amy.

"Don't start," the Doctor scolded Harkness.

"Amelia Pond," Amy said.

"Williams," Rory corrected her.

"Right," Amy said with her eyes closed, embarrassed.

"I'm Captain Jack Harkness, pleased to meetcha ma'am," Harkness said with a charming smile that could melt the heart of any woman. "So you're married?"

"More or less," Amy said, smirking at him.

"I like the sound of that less part," Harkness said, smirking back.

"I bet you do," Amy returned.

"I'm standing right here," Rory said, exasperated. "Right. Here."

"Wouldn't be the first time I've been involved with a married couple, both spouses," Harkness said shamelessly.

"Ok!" The Doctor finally interjected. "We've got a world to save remember."

He grabbed Amy's shoulders and steered her to Rory's side. She smiled at him guiltily as he looked a little annoyed.

"Rory, keep her close," the Doctor instructed. "All of you, follow me."

The Doctor began walking down the corridor. Amy and Rory stepped to followed.

"Doctor?" Harkness shouted. "It's this way."

The Doctor strode back into the room and down the opposite corridor.

"I knew that," the Doctor said quickly.

The Doctor walked quickly. Harkness matched his stride easily but Amy and Rory had to work to keep up with him. Amy noticed how Harkness walked a step behind the Doctor, as if he were a subordinate of the time lord as well. There was something more mixed in though. The way they spoke to each other, the way they acted around each other, it was almost as if they had known each other all their lives.

"How long have you two known each other?" Amy asked, curious.

"A little over 2500 years," Harkness answered first.

"Are you that old now?" The Doctor asked in surprise.

"I had a little incident, I forgot to tell you about it the last time I saw you," Harkness answered.

"Blimey," the Doctor said, still shocked. "You're older than me now. I've only known you a few hundred."

Rory was flabbergasted at how they were throwing out such large numbers as if they were arbitrary. Then he remembered, when it came to the Doctor, age and time was arbitrary.

They turned a corner and Harkness pressed his thumb against scanner at the side of a door. When they entered, Amy and Rory were taken aback by the amount of computers and various machines that filled the room. Along two opposite sides, adjacent to the door, were a row of monitors, all with people sitting at them. There were two large screens above the monitors that showed an image of the globe with a small orange dot bouncing all over it, the other showed various graphs and charts that neither of the two could understand. On the far side were larger computers and a small bank of servers. The whole room had a very clean feel to it. It was very mechanical and lifeless. Even the people in the room seemed a bit like zombies, mindlessly watching their computers.

The Doctor strode into the room and immediately looked at the graphs and charts on the right large screen. He studied it for a few seconds before moving over to the other one.

"Atmospheric conditions seem normal, no changes in weather patterns, no unusual sightings, nothing," the Doctor said, sounding frustrated. "It's like nothing has changed, nothing out of the ordinary. If anything, it's too perfect."

Harkness stepped over to Amy and Rory. Once again, Amy's eye was trained on him, unable to move away.

"For a man with such amazing intelligence," Harkness began. "He sure misses a lot of the most basic things."

"Oi," the Doctor shouted. "What's that supposed to mean?"

Harkness stepped away from the pair and into the middle of the room. He looked around suggestively. The Doctor also looked round but saw nothing. Harkness sighed.

"We're under attack!" Harkness shouted out. "Everyone, prepare for invasion!"

Nobody moved.

"I'm going to strip completely naked!" Harkness shouted again.

Amy made a sound that could only be described as a squee, but nobody else moved. The Doctor looked at the people. He saw them all. They weren't just diligent workers, they were mindless. They were unresponsive. He was horrified by it and he was annoyed at himself for not noticing before.

"Do you know what's going on?" The Doctor asked, still looking at the people.

"Honestly, we were hoping you'd tell us," Harkness said, looking dismayed.

The Doctor moved to the nearest person and scanned her with his sonic screwdriver. When he flicked it up and read the readings, he felt even more annoyed. There was nothing. The person was exactly as she should be. There were no abnormal readings that suggested mind control, nothing to suggest they had been attacked, they were normal.

"Wait a minute," the Doctor said, realising what Harkness had said. "We?"

"I finished the sweep, everybody is the same, even the director," another American voice said.

A medium build black man with short hair came into the room. He was dressed smart, in a shirt and jacket, but there was something about the way he held himself that suggested he was a little rough, and had previously been injured.

"Ah," Harkness said. "Doctor, Amy, Rory, I'd like you to meet Rex."

Amy and Rory waved, but the Doctor looked at Rex with worry. He stepped over the Harkness with a calm face. Except, it was that calm face that came before the Doctor did or said something in anger.

"Jack," he began, still calm. "Would you mind, please, explaining to me why there are two of you?"

"Two?" Amy asked, looking between the two. "They couldn't be further from each other."

"He means that we both can't die," Harkness said simply.

"Is this the guy you told me about?" Rex asked, looking disapprovingly at the Doctor. "Isn't he a little weedish?"

"Oi!" The Doctor shouted. "I don't want that cheek from someone like you."

"Doctor," Harkness said quietly. "It isn't his fault, and I told you not to be prejudice against me."

"Hold on!" Rory said loudly. "What do you mean you both can't die?"

Harkness sighed. He pulled out his service revolver and shot Rex in the head as if it were nothing. Amy screamed and jumped backwards and Rory jumped in the way of Amy and Harkness. The Doctor wasn't surprised, but jumped at the sound of the gun.

"What the hell do you think you're doing?" Rory shouted.

There was a gasp from Rex as he woke up and rose to his feet. He looked annoyed at Harkness.

"What've I told you about doing that?" Rex said, frustration thick in his voice.

"Look, this doesn't matter," the Doctor said. "We don't have time for this. I don't know if you've noticed but we only have 22 hours and 45 minutes to save the world and we still don't know what's going on."

Rex breathed deeply, crushing his anger, saving it for a later date. He stepped over to one of the computers under the screen that showed the globe. Amy and Rory looked in horror as the back of Rex's head healed in front of them. The Doctor and Harkness stepped over to the screen.

"What about the TARDIS?" Harkness asked. "Can't we get help from her?"

"She's gone," the Doctor said darkly.

Harkness saw his expression and knew not to ask. He'd ask later when things weren't so urgent and when he'd have time to explain properly.

"A little over an hour ago I got a message on my manipulator, saying the world would end in 24 hours. I followed the signal back but it led me to a field in the middle of Singapore. So, instead, I came back here. That's when I realised everyone was acting like robots. So far, I've not been able to work out why. I tied my manipulator into the control systems here to trace the signal, but it keeps moving. That orange dot is the signal, it moves every millisecond. If I didn't know any better, I'd say it was coming from all these points at once and we just don't have the capacity to track it," Harkness explained.

"So you've still got your manipulator?" The Doctor asked. "Good, we'll need that. Fastest way to travel without the TARDIS."

"Sorry, what's a manipulator?" Amy asked, completely confused.

"A vortex manipulator," the Doctor answered. "It's a truly terrible way of travelling through time and space. It's cheap and tacky."

"And this is the second time I'll have used it to save your ass," Harkness retorted.

"I thought I disabled it," the Doctor said, curious.

"I met a woman on a planet who knew how to fix it," Harkness explained.

Amy and Rory both looked at each other and smiled. The Doctor, however, frowned. They knew who it was that had fixed it. The same woman that was always the reason that the Doctor's work was undone. Professor River Song. Ignoring this, the Doctor started working. He cycled back through the information on the screens, trying to find some anomaly, something that would explain what had happened.

"I've done all that," Harkness explained. "I've searched everything, but nothing explains it. Nothing says what's making the signal and nothing explains what's happening to people. There is even less to explain how the world will end."

"Be funny if it was the core," Rory laughed.

Harkness and the Doctor turned and stared at Rory.

"Sorry," Rory immediately said. "I was just thinking, the only place every point on that map has in common is the core. If the core of the planet was where the signal was coming from, it might explain why it was coming from everywhere. But, I'll just shut up now."

"Rory," the Doctor said, walking over to the man.

Rory braced for a scolding. He closed his eyes in anticipation. The Doctor kissed him on the forehead.

"You are brilliant!" The Doctor shouted.

"I don't know why I didn't think of that," Harkness agreed, laughing. "Well done kid."

"Not a kid," Rory retorted.

"Get your manipulator, Jack, we're going on a journey to the centre of the earth," the Doctor said gleefully.

"But, Doctor, isn't it just molten lava down there?" Amy asked, confused again.

"When the planet was first created, a ship flew in. It is the core," the Doctor explained. "Be warned though, the pressure will give you a bad headache, we can only stay for a short time, and it will be quite hot."

Harkness strode over, his vortex manipulator on his wrist.

"We're ready, Doctor," he said, grinning. "Everyone grab hold."

Amy, Rory, Rex and the Doctor touched the Vortex Manipulator. Harkness smiled as he thought of something funny.

"Been a while since I had this many people touching me," Harkness said with a cheeky smirk.

"Just press the button," the Doctor said, exasperated.

Harkness pressed the button. All five of them felt a nauseating pull as they were yanked into the time vortex by the small manipulator, heading towards the Racnoss ship at the centre of the planet.