Passwords are, by their very nature, hideously complicated. Some passwords are just a sequence of characters, for example '1234jJ,iE'. Some, however, are sounds or a vocal message. They can work on many levels, including ultrasound. These passwords are notoriously hard to crack. Charles Yu knows this. He also knows that if he doesn't crack this particular sound password within the next five minutes and get the power back online, he and his two surviving team members will drown due to the rising water.

'Come on, Charles! We don't have long!' shouted Major Patrick Reese. He raised his assault rifle and fired at the creatures that were emerging from the water around them. Reese was a small man, Irish, and 45. He had recently had a son with his wife, and had been looking forward to seeing them both. He had named him after his grandfather, Jonathan. They were standing in the middle of a large room, on a podium that had been about two metres above the ground. It was now a foot above the rising water. The room itself was part of an underground research facility. It was the size of a hangar. The lights had gone out, so the team were seeing by flares. Charles was standing next to a computer at the edge of the podium. Occasionally, some water shot up and splashed the surface of the podium. Charles himself was gangly, Asian-American and a computer expert. He had been brought in to look into the recent problems that the facility had been experiencing. He was 27, and had been the youngest member of the team. Dr. Andrew Late, the third survivor, was watching the ceiling with a worried expression on his face. He was worrying about the roof above their heads. It was very likely to break open soon, and when it did, thousands of tons of water from the above floors would come spilling into the room. Andrew Late was English, a medial doctor and an expert in biology. He specialised in the rather stranger side of biology. Mutations and so forth. He had in fact been brought to this place because of that. Andrew sighed. Being 52, and easily the most senior member on the team, he knew he was far to old to be doing this. But, as he told himself at times when he doubted his career choice, especially the one that led to his being in an underground research facility on a planet with an unknown name, thousands of billions of miles from Earth, joining the SGC, Stargate Command, he knew one thing and one thing only: this was the experience of a lifetime.

Charles tapped away at the buttons on the keyboard, piecing together sounds to make a continuous, for want of a better word, tune. He suddenly stopped shouting.

'Major! I think I've got it!' He shouted above the sounds coming from around him. Reese paused and turned around while reloading.

'Well, get on with it lad! We don't have all day, you know!' He heard something emerging from the water, turned towards it and put a couple of rounds into it.

'Here goes nothing.' Charles said, and pressed a button. Immediately the entire room was filled with a noise, unlike anything any of them had heard before. It pulsated through the room, echoing again and again and sounding like a bee on caffeine trying to play a trumpet, xylophone and harmonica, all at the same time. It was very disturbing and migraine-inducing. Reese covered his ears. He tried shouting to Charles and Andrew, but no sound came out of his mouth. Suddenly, the noise stopped. There was a small buzzing, then the lights came on.

'Good job, lad! Let's move!' Charles immediately started pressing buttons on the computer. He waited a few seconds, and then heard it.

Kawoosh!

The stargate had opened up. It rose up out of the podium, the watery middle looking spookily like water gathering around their feet. Charles typed in the iris code on his GDO, and was ready to leap into it, when he heard a familiar noise. A creature, looking akin to a watery zombie, rose out of the water. These creatures had been the cause of the problems in the facility, and they were highly aggravating. Notably because of their power. They could rip through trinium if you gave them the chance. Thankfully, Charles never gave the creature one. He pulled out a zat gun and shot it. The thing shuddered, expanded and exploded. Charles then turned and ran through the gate. Reese put a few rounds into the other creatures and followed suit, grabbing Arthur's arm and pushing him through. Just before leaving, he pressed a button on a remote control, then jumped through the gate. After five seconds, the gate shut down. After ten seconds, the facility exploded.

'Hello? Anyone? Is this some sort of sick joke?' Reese shouted. He looked around. Like the facility they had escaped from, the lights were out. Just to test, Reese waved his hand in front of his face. He was surprised when he couldn't see even a hint of it. He got a flare out of his pocket and lit it. Andrew and Charles were looking around. The place wasn't as big as the facility's room, but it was still awe inspiring. There were carving all around the walls. They appeared to depict a great battle. Reese looked at them and tried to figure out against all hope who was winning.

'You sure you dialled the SGC, right?' No response. 'RIGHT!'

'Yes!' Said Charles. 'I did dial it! Don't blame me for this!' He appeared to calm down. 'Look, this place was obviously built by an intelligent race. There are messages in hundreds, maybe thousands of languages here! This could've been built by the ancients! We have to get someone!' Charles looked around. 'Speaking of that, where's the stargate?' Reese looked around. Charles was right. The stargate had actually disappeared.

'PERFECT!' Shouted Reese. 'Just bloody perfect! Now we're stuck here. As a matter of fact, I don't even know where 'here' is!'

'We're on Perpetua.' Andrew said from a wall. Reese spun around and directed his anger at Andrew.

'Oh? And how do you know that?' He said furiously. Andrew pointed to a section of the wall.

'It says it right here.' He pointed to the wall.

'But you don't know ancient languages, so how can you translate it?' Charles asked.

'It's in English.' Andrew said simply. Reese and Charles gathered around. Sure enough, where he had been pointing, there was a message engraved in English. It read: "Welcome to Perpetua. Press HERE to enter." Reese looked at the message.

'Subtle.' He said, before pressing on the word HERE. It slid in like a button. The wall shook and opened into a doorway. Reese hesitated before opening it. Beyond it was a large balcony. The three men walked over the edge and looked around. What they saw made them stop in their tracks. They saw a large valley that had been converted into a shipyard. For spaceships. There were hundreds lying around, broken or charred, abandoned by the mists of time. There were a few spaceships in orbit and - this made all three of them, Reese, Charles and Andrew, fall back in shock and astonishment - there was a giant spaceship covering the sky. It was gigantic. They all appeared to be derelict, however. Reese looked at the other two, amazed at what he had just seen.

'I don't think we're on Earth…'