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Korra lead the way down the ramp from the Renaissance to the landing platform, where a man and woman dressed in green robes were waiting. The woman was tall and graceful, with a serious expression, while the man wore spectacles and a neatly trimmed beard.

'Welcome to Zaofu, Avatar Korra,' the woman said and Korra stepped forward, bowing with her hands clasped in front of her.

'Thank you, Suyin,' Korra said, and Suyin stepped forward to enfold her in a hug.

'It's good to see you all again,' she said, hugging Asami and shaking hands with Bolin and Mako, before turning to Tenzin.

'Greetings, Master Tenzin,' she said, taking Pema's hand and giving it a squeeze. 'It's good to finally meet you, Pema...'

'Thank you,' Pema said, with a smile and Suyin turned to Milo, Jinora, Ikki and Rohan.

'Hello,' she said. 'While you're here, I want you to think of this as your home...'

'Thank you,' Jinora said, as Milo stepped forward, looking up at her with a focused expression.

'You're nicer that Chief Beifong,' he said, Ikki stifling a laugh and Rohan rolled his eyes.

'Thank you,' Suyin said, as Tenzin cleared his throat.

'Do you have any more information?' He asked and Suyin nodded.

'We've been monitoring the situation since we received your message,' Suyin said. 'Please, follow me...'

She turned away and the others followed her, Korra glancing over her shoulder to see that Jinora was still standing on the landing platform.

'Jinora? You okay...?

'Hmm? Sorry, Korra. It's just...I felt something...' she said and Korra frowned.

'Like what...?'

'I'm not sure. Some strange, like a spirit portal, but different...'

'Alright,' Korra said, putting a hand on her shoulder. 'Come on. Whatever it is, we'll figure it out...'

#################

'This is our Operations Centre,' Suyin said, leading them into a circular room that was dominated by a large map table. Two dark-haired young men stood by the table, both dressed in similar robes to Suyin. 'You remember my eldest sons, Wei and Wing. They've been monitoring and recording the transmissions that we've received. Wei...'

'Judging by the strength of the signals, we've determined that the source is approximately 3 kilometres away. However, we have no way of knowing the direction of that source...'

'We might be able to help, there...' Asami said. 'We've got some prototype radio receivers onboard the Renaissance that we can use to trace the source...'

'Could we listen to the transmissions you've recorded?' Mako asked. 'We might learn something from them...'

'Of course,' Suyin said and Korra turned to Jinora, putting a hand on her shoulder.

'We...might have another lead...'

#################

'You think it was a disturbance in the Spirit World?' Tenzin asked and Jinora nodded.

'I think so...'

'There's only one way to find out,' Korra said, as they entered the Meditation Garden. 'We'll need to enter the Spirit World...'

Sitting down with her legs crossed, Korra closed her eyes, taking a deep breath to slow her breathing and she felt the familiar sensation, like her body was falling away. When she opened her eyes again, she found herself standing next to Jinora and Tenzin on a green field, tall trees stretching above them.

'Where are we?' Tenzin asked and Korra shrugged.

'I'm...not sure...'

'We're near Wan Shi Tong's Library,' Jinora said. 'I think he might be able to help us...'

#################

'Dispatch Central to FD-578. Warehouse fire in Quadrant Sierra-9...'

'Acknowledged, DC. FD-578 responding...'

Hitting the stop button on the recorder, Bolin sat back with a groan as he took off his headset, tapping Mako on the shoulder, who held up his hand without looking round.

'Come on, Mako,' Bolin said. 'We've been doing this for two hours and we haven't learnt anything, except that this place has a lot going on...'

'Yeah,' Mako said, taking off his own headphones and sitting back. 'But, the number of messages tells us something. Since the Future Industries airship detected the first transmission, Zaofu has recorded over 5000 individual messages, which suggests that they're coming from a large city...'

'But, there's no other city around here other that Ba Sing Se and it's too far away to be the source. So, unless there's a hidden city around here, somewhere...'

'I think we'd have noticed, bro,' Mako said, with a grin. 'Hopefully, one of the messages will give us a clue...'

With a sigh, Bolin put his headset back on, pressing the play button again...

#################

'So, where is this Wan Shi Tong?' Korra asked as they stepped inside the library, looking around at the dusty shelves that stretched further than they could see.

'He'll be here,' Jinora said, just as there was a beat of wings and a black owl with a pale face landed in front of them. Twice as tall as Korra, his beak clicked as he looked from her to Tenzin, his eyes settling on Jinora, who bowed.

'Good day, Wan Shi Tong...'

'Jinora,' Wong Shi Tong said, turning his head to focus his eyes on her. 'What brings you back to my library...?'

'We have come to ask for your help,' Jinora said. 'These are my friends...'

'Avatar Korra and Master Tenzin,' Wan Shi Tong said. 'What help can I provide to the Avatar...?'

'We've been detecting strange signals in our world,' Korra said. 'And Jinora sensed a disturbance here in the Spirit World. Do you know anything about that...?'

'I may,' Wan Shi Tong said. 'However, I do not provide information for nothing. I will only trade it for knowledge of equal value...'

'This disturbance might threaten your world, too...' Korra began, but Jinora stepped forward.

'Right now, we don't know where these signals are coming from. No-one does. When we find out, we will share that information with you...'

'...very well,' Wan Shi Tong said. 'A human came here, bringing me information on the existence of another world separate from yours and mine. He traded this information for a scroll that he was searching for...'

'Do you know which scroll?' Tenzin asked and Wan Shi Tong clicked his beak, a raven fluttering over with a scroll clutched in it's feet. The raven dropped it on the table and Tenzin picked it up, removing the seal and unrolling it.

'What is it?' Korra asked and Tenzin turned towards her.

'Something...that concerns me. We need to return to Zaofu...'

#################

Korra opened her eyes to see Suyin sitting in front of her, a tray sitting on the ground next to her.

'Here,' she said, picking up the teapot on the tray and pouring three cups, handing one to Korra. 'You must be thirsty...'

'Thanks,' Korra said, accepting the cup as Suyin handed the others to Tenzin and Jinora.

'How long were we gone?' Tenzin asked.

'About two hours. Did you find anything?'

'Not sure,' Korra said. 'Tenzin...?'

'Perhaps,' Tenzin said. 'I need to check some of my books. I'll join you in the Operations Centre...'

#################

'Sorry I'm late,' Asami said, as she stepped into the Operations Centre. Korra, Mako, Bolin and Tenzin were already there, as well as Suyin, Wei and Wing. 'I was making some adjustments to the Renaissance's radio receivers. What's going on...?'

'We went to Wan Shi Tong's Library in the Spirit World,' Tenzin said. He told us that a human came there looking for a scroll...'

'Just one scroll...?' Mako asked. 'What's so important about it...?'

'It contains an ancient Fire Nation legend,' Tenzin said. 'About a powerful firebender named Tacon who learnt how to open a portal to another world...'

'You mean...the Spirit World?' Bolin asked and Tenzin shook his head.

'No. Another human world, different from our own, but connected. Tacon was a firebender who had visions of this other world and he became obsessed with finding it. Determined to discover if his visions were true, he spent several months in the Spirit World, where he learnt that there were...weak points in the walls of the world. According to the legend, he found one of these weak points and opened the portal...'

'...Tenzin,' Suyin began. 'Are you saying that you think someone else has opened a portal to this...other world...?'

'We cannot discount the possibility...'

'Either way,' Korra said. 'We need to find where the signals are coming from. Everyone, get some sleep. We'll leave first thing tomorrow...'

#################

'These will be your rooms while you're here,' Suyin said, . 'They're...a little basic, but you should both be comfortable...'

'I...we...' Korra began, her cheeks heating up and Suyin smiled.

'It's alright, Korra. I'm happy for you and you have nothing to be ashamed of,' she said. 'I'll see you in the morning...'

#################

Tenzin tucked Milo in, slipping out and closing the door quietly behind him.

'They're all asleep,' he said as he crossed the hall to his room, where Pema was already in bed. Slipping out of his robe, he got into bed next to her as she shuffled over to make room for him.

'Do you think it's true?' She asked. 'That this...other world does exist...?'

'After everything we've seen, I cannot discount the possibility...'

'Hm. Either way, I hope it's not true. We've got enough troubles to deal with in this world...'

#################

Korra woke with a groan as there was a knock at the door, sitting up with the blankets clutched to her chest.

'...what is it?'

'It's morning, Korra,' Tenzin said and she felt a blush rising to her cheeks.

'...right, right,' she said. 'We'll be there in a few minutes...'

She waited until Tenzin's footsteps retreated, reaching over to shake Asami by the shoulder.

'Come on,' she said. 'We need to get up...'

Asami grunted, rolling over as Korra slipped out of bed, grabbing her clothes from the floor.

'Uhh...what's the rush...?'

'It's morning. Come on, we need to get moving...'

'I'd get moving a bit faster if someone hadn't keep me up until past midnight...'

'What can I say?' Korra said, grabbing Asami's underwear and throwing it to her. 'I can't help it if you're irresistible...'

#################

'What are we doing?' Milo asked, stifling a yawn as he lounged in one of the chairs in the lookout dome above the bridge.

'We're going to try and locate the source of the signals,' Jinora said, without looking up from the book that she was reading. 'By recording the strength of the signals from three different locations, we can plot a series of concentric rings that should help us to localise it...'

'Okay...' Milo said, his brow furrowing in concentration. 'I don't get it...'

'It's like listening to a sound from several places to work out where it's coming from,' Rohan said and Milo grinned.

'Got it...'

'What are they talking about down there?' Ikki moaned, from where she was pressing her nose against the glass, staring down at the bridge. 'Come on, let's get going...'

'Settle down, Ikki,' Pema said, tightening the straps on her chair's harness. 'We'll leave in a few minutes...'

#################

'Alright,' Asami said, as she sat in the Renaissance's pilot's seat, running her hands over the controls, flipping switches and adjusting dials. Mako, Bolin and Tenzin were already seated at the sensors stations at the back of the bridge, while Korra hovered over her shoulder.

'You should sit down,' Asami said, gesturing to the empty co-pilot's seat. Korra hesitated before slipping into the chair and fastening her safety harness as Asami powered up the engines. With a faint hum, the Renaissance rose of the ground, moving away from Zaofu.

'We're approaching the first set of co-ordinates,' Asami said, glancing over her shoulder at Mako. 'Are you getting anything...?'

'Hold on,' Mako said, pressing his hand to his earpiece. 'Yeah. Here we go. Bolin...'

'Got it,' Bolin said. 'Signal strength puts it at around 5 kilometres away...'

'Alright,' Asami said. 'I'm setting course for the next co-ordinates. We should be there in about 20 minutes...'

'Let's hope this works,' Korra muttered and Asami grinned.

'It'll work,' she said. 'Would you like to take the controls for a while...?'

'Uhh...'

'It's alright,' Asami said. 'I trust you...'

'Okay. What do I do...?'

#################

'There you are,' Asami said, as they moved away from the second set of co-ordinates after taking the signal sounding. 'You're getting the hang of it...'

'If you say so,' Korra muttered, maintaining her white knuckle grip on the controls, just as Milo called down from the observation dome.

'Look. Another airship...'

'What...?' Asami said, her head whipping round to see a black shape outlined against the sky. 'Where did that come from...?'

'It just appeared on our scanners,' Mako said. 'And it looks like they're heading towards us...'

'Everyone strap in,' Asami ordered, as the airship drew closer. Now that it was nearer, she could see that it has been painted dark red, with a stylised flame emblem on the side. As she watched, the hatch on the side opened, revealing figures dressed in rough clothes and crude metal masks. One by one, they leapt from the airship, fire igniting from their hands to launch them onto the deck of the Renaissance.

'Take over,' Korra said, unbuckling her harness and scrambling up from her seat.

'Hey,' Asami yelled, grabbing the controls as Korra moved towards the hatch that lead out onto the deck, followed by Mako, Bolin and Tenzin. Shouldering the door open, Korra thrust out her hand, a blast of air knocking one of the firebenders back into the hull. Mako charged past her, launching into a spinning kick that caught another firebender across the face, knocking his mask off. Springing over the unconscious man, Mako unleashed a fireball that knocked another firebender over the edge and he would have fallen if he hadn't used his bending to blast himself back into their airship. Meanwhile, Bolin was wrestling with muscular firebender who had him in a headlock. Breaking the grip, Bolin shifted his weight, slamming him to the floor with a shoulder throw. A portly firebender charged at Korra, a fireblade extended from the back of his fist. Dodging back, Korra caught him in the stomach with a kick that lifted him off his feet. Springing back to his feet, he launched a stream of fire towards her and she moved her arms in a circle, gathering it into a ball and sending it back at him. The ball struck him in the chest, his heavy leather clothes protecting him from the heat, but it sent him staggering backwards.

'Fall back,' he growled, vaulting over the edge of the railing and blasting back to the deck of their airship, followed by the remaining firebender. The hatch of the airship ground shut and it began to turn away.

'No, you don't,' Mako said, launching a fireball that took out one of their engines.

'What?' He said, seeing the other's expressions. 'They should be able to land safely...'

'What do you think that was about...?' Bolin asked and Korra shrugged.

'No idea. We'll radio Zaofu and ask Suyin to send out a search party to look for survivors. Maybe that way we can find some answers. And we have a job to do...'

#################

'Come in, Renaissance...'

'Go ahead...' Mako said, pressing his hand to his headset.

'This is Wei. We've reached the airship crash site and we've got the crew in our custody. We'll take them back to Zaofu until we can turn them over to the United Forces...'

'Thanks,' Mako said. 'We should be back in under two hours. Renaissance out...'

'Approaching final co-ordinates,' Asami said. 'Bolin...?'

'Got it,' Bolin said. 'Looks like the signal is coming from 2 kilometres away...'

'Alright,' Asami said, getting up and moving over to the map board at the back of the bridge, plotting the three signals on the chart. 'That looks like an area of about two miles...'

'So, now what?' Bolin asked.

'Now, we search on foot,' Asami replied.

#################

The Renaissance touched down, Korra leading the others down the ramp and looking around.

'Jinora? Can you sense anything...?'

'Yes,' Jinora said, closing her eyes for a moment. 'This way...'

She lead them across the grass into a small grove, stopping and turning in a slow circle.

'It's here,' she said and Korra closed her eyes. The air seemed to hum with a faint sense of power.

'Alright,' she said. 'Everyone stand back...'

After a moment, the others backed up a few paces and Korra took a deep breath, her eyes glowing white as she entered the Avatar State, a white hot rush of energy spreading through every cell. Stepping forward, she extended her hands and pulled them apart, a rip appearing in the air in front of her. As it stabilised, she found herself looking at a dingy street, the corner piled with rubbish. She glanced over at the others, turning back to see a shabbily dressed man walk past. He stopped when he saw them and Korra quickly sealed the portal, turning to the others.

'Well, we've found it,' Asami said. 'What now...?'

'Isn't it obvious?' Korra asked. 'We're going through...'

'I thought you might say that,' Asami said, with a smile. 'Come on. I've got something to show you all...'

#################

'I thought that things would move quickly, so I put these together,' Asami said, picking up a compact grey pack and putting it on the table with a thump. 'Survival kits. Blankets, water, emergency rations and a small medical kit. Also, there's these,' she added, picking up a small white box and opening it, revealing eight curved, silver objects. 'Miniaturised radios. Short range and experimental, but they should let us keep in touch...'

'This is great,' Mako said. 'But, what are we actually going to do...?'

'We either need to find the firebender who went through and convince him to come back with us, or we need to close the portal permanently. Make whatever preparations you need. We'll leave in an hour...'

#################

'You're going,' Pema said, as she closed the door behind her, Tenzin looking up from where he was packing.

'I have to, Pema. Korra needs me...'

'So do we, Tenzin,' Pema said, sitting next to him. 'You've helped Korra grow into a strong Avatar, but you have other responsibilities, now. Here, with your family...'

'You're right,' Tenzin said, with a sigh. 'I've tried to deny it, but you're right. Korra doesn't need my help. Not anymore...'

'That's something to be proud of, Tenzin,' Pema said, kissing him on the cheek.

Thank you for reading. I hope you enjoyed it. Any reviews, comments or constructive criticisms are very welcome.