For Sineater and the angstober prompt 12: "Help Will Be Here Soon. I Promise." With Virgil and Penny.

I owe a big debt of thanks to Tsari, who talked me through this, helping to get plot points in line and made suggestions, and Gumnut, who made me promise to fix Virgil in the end…eventually. And then we remembered this is angst…

Spoilers for Signals part 2. All the speech in italics is directly from the episode. We get to where the fic divulges from the episode at the '...'

'I've never seen anything like this. The sea floor is pulling us in.' Scott frowned, trying to keep Four's hold on the escape capsule, throttling the submarine backwards to no avail.

'It's sea sludge. This stuff is seriously bad news,' Gordon replied. 'It's like quicksand but even worse. If the capsule gets sucked under, we may never get it back.'

Scott wasn't about to let that happen. 'But we need the escape capsule's camera. It's our only way of finding Dad.'

'I'm sending down the rescue claw.' Virgil joined the conversation. Scott could picture the giant claw descending from Two's belly. 'Er…We have a slight problem.' Scott held his breath.

'You're too deep. The claw's not going to reach.'

'Tray to hang on a little longer,' said Penny, trying to reassure him. 'We'll find another way.'

'I'll do my best.'

Virgil made his way down to the bay, looking to find some way to extend the cable, but he soon returned. He sighed. 'There's no way to extent the cable,' he told Penny. Sitting back down in the pilot's chair, he addressed Scott.

'Scott, you're either going to need to let go of the capsule or get sucked down into the sludge along with it.'

Not what any of them wanted to hear, so when Penny pipped up everyone was listening.

'There may be one other option. What we need is another submarine. Why don't we use Thunderbird Two?'

'Well, for starters, this isn't a subma…Wait a minute. Why don't we?!' Penny and Virgil exchanged glances. 'Brains, can Thunderbird Two operate under water?'

Brains replied immediately. 'Well, yes, technically it can, but not without considerable challenges, including m-mortal danger.' They could hear the worry that was clear on his face.

'We're going under.' Virgil turned to Penny. 'See what you did there? Thunderbird Two IS a submarine.' Penny smiled back.

'Well, whatever you have to do, do it fast. I don't have much more time!' Scott's voice echoed the strain he was under, and Virgil and Penny got busy.

Brains talked them through everything and Virgil landed on the surface of the sea, flooding the module so Two began to sink.

'Thundersub Two is Go!'

They descended steadily, ten metres per second. It took time, and at almost halfway Two began to take on water. Virgil gave Penny the helm while he went to look, not that he had any idea what he was going to do.

Wing it, like any good Tracy would.

Of course, this was the precise point that Scott told them he was being pulled under. While Penny tried her best to reassure him, Virgil was busy flipping switches. Leaks in all four landing strut housings. He prayed that the temporary fixes would hold. The priority to get Scott was now overriding everything else.

A little wet wouldn't hurt them. He hoped.

'Virgil, I hope you've got a brilliant idea, because I am all the way under.' That was not what Virgil wanted to hear, and he rushed back to the cockpit.

'Deploying grasping claw. It should be close enough to reach you now.' He fired the VTOL to counteract Two's motion, and they watched the display as the claw sank into the sludge.

'Come on. Come on,' Virgil spoke to himself, but Penny echoed the sentiment in her mind. 'Scott, the claw's under. Can you see it?'

Scott looked, but he couldn't see anything in the sludge. It was pitch black. When he relayed back to Virgil that he was 12 metres below the seabed and still falling, Virgil bit his lip.

'Hang on. I'll find you.'

Penny watched Virgil as he watched the holographic claw descend even further. 'Where are you?' he muttered to himself, but Scott must have heard because he answered.

'Readouts show me 20 metres under the surface.' He must be close now, surely? 'Virgil, stop!' His reaction was immediate, years of working together honing such instincts. 'You just made contact. Close the grabbing claw.'

'Ok, but I'm going in blind!'

'That's it! I think you got me.'

'Only one way to find out.'

He reversed the thrust and Scott called out descending numbers. It was music to Virgil's ears.

'19 metres. 18 metres. Unless I'm magically rising on my own this is working.'

Virgil took it slowly, explaining to Scott that if he went too fast the sludge would crush the capsule. No one wanted that.

At this exact same moment, Kayo and Alan had at last managed to get onto Three. Alan activated the manual override and at last they were back on board.

Brains groaned. Three was still in Havoc's hands, Two was very slowly rising and pulling Four out. Surely nothing could go wrong now?

The alarm sounding on Two told him otherwise. Power was failing on Two, the VTOL's stuttering. The sludge was acting like concrete. And then they stopped. There wasn't enough power to pull Four anymore. They were risking engine burnout.

'It's not worth it Virgil, I'm going to release the capsule.'

'Scott, no!'

'We can't risk losing Thunderbird Two. Or the both of you.'

'You let us worry about that. We are not missing this one chance to find out what happened to Dad.'

...

'Come on, baby. Just a little more.' Virgil was trying everything. The VTOL stuttered again, then died completely. They sank that last little bit onto the bottom of the sea.

'Er, Virg? I'm being pulled under again.'

'Engines have failed, Scott. Two's on the floor.'

'Is she being pulled under too?'

'Negative. At the moment she's just resting on the top, but if I try to move her now, I risk that happening.'

There was silence over the comms.

'Brains?'

'Y-Yes, Scott?'

'Can Three pull us out without risking Two getting caught in this sludge?'

'Er, y-yes, she's powerful enough and the cable is long enough.'

'But? I can hear there is a but.'

'B-but Thunderbird Three is currently in Havoc's control.'

The silence at that was more deafening than if Scott had shouted.

The floor shifted and two sank just a little. Enough that Scott registered the change. He was now at 21 metres, which could only mean one thing. Two had begun to sink.

'Can Two risk winding the claw in?'

'No' Both Brains and Virgil spoke at the same time.

'If I let go of the canister will that change?'

'No.' This time it was just Virgil, and he was very quiet. Penny glanced at him, concerned. Virgil had closed his eyes. He knew exactly where Scott was going with this reasoning.

'Will Two stop sinking if you cut the claw loose?'

There was a possibility, if Two hadn't sunk enough into the sludge, but there was no way, no way that he was going to do that.

'No, Scott. There's no guarantee of that.'

'But there is a possibility?'

'No.'

'We can't afford to lose all three of us. Not wh…'

NO! We can't afford to lose you either!'

'Virg.'

'NO! No, you can't suggest that.'

'I can and I will. It's the risks we all take.'

It was so gently spoken that Virgil couldn't help the sob that he let out. Penny reached across and placed a hand on his arm. She looked at Virgil as she spoke, but it was addressed to both of them.

'Help will be here soon. I promise.'

She had no doubt of that. The Tracy's had proved time and time again that they could defy the odds. She saw no reason not to doubt that now.

Virgil placed a hand over Penny's and smiled weakly at her, nodding.

'Just hold on a little longer, Scott. We're working on it.' Scott didn't reply. Virgil frowned. 'Scott?' Still nothing. 'Brains, I can't get hold of Scott!'

Brains and Gordon appeared before him, alongside an outline of Four. She was still being pulled down, even though Two seemed to have stopped. The cable was still playing out.

'Scott must almost be out of oxygen. We hadn't gambled on Four going so deep.'

'But Four has travelled deeper before!'

'Yes, but she's still new. And the added pressure of the sea sludge creates more issues.'

'The cable is still playing out, Virg.'

'Yes, I know that, Gordon.'

'Shouldn't you stop it?'

'If I stop it, then I risk that pressure increasing on Four and imploding her.'

'But if he gets much further then Three may not be powerful enough to pull you both out.'

'Three has her ion engines. I think that this would constitute a big enough emergency to use them if needed.' Brains didn't stutter once through that, which told them it was a serious consideration. They just needed Three back.

Penny stared at the view. There was a niggling thought in the back of her mind, one that she really didn't want to voice as it would only increase the family's worries. She was pretty sure in herself, though, having boarded Two with Scott.

The man hadn't brought his helmet with him.

If Four was losing oxygen and Scott didn't have his helmet, Penny wondered if he would either have the time or be aware enough to grab one of the spares she knew Four always carried. She stole a casual glance at Virgil. The man was tense enough without her adding to what he was already facing.

'Kayo and Alan won't let us down,' she said quietly. 'Help will be here soon, Virgil.' He gave her a look but couldn't manage even a weak smile to answer.

'Thunderbird Three to Tracy Island. We have our ship back!'

'Alan, this is Five. I'm sending you Virgil's coordinates. You need to get there now, Alan!'

Alan and Kayo exchanged glances as Alan turned Three around to the corrected coordinates and punched it. John filled them in as the rocket powered through re-entry at a speed Alan would never normally try.

It felt like hours later, but within minutes there were thunks as Three latched cables onto Two.

'Al, slow and steady, alright?'

'But Virgil, Scott's been down there too long!'

'If you go too fast you'll cause the sludge to solidify and we'll never get him out!'

Alan gulped. No pressure there, then.

The nose of the rocket was in the water, but her engines were clear, and Alan kept a steady pressure. Three whined with the unusual strain, and he began to engage the ion drive. Keeping the pressure steady was harder than it looked, and soon Alan's arm was trembling.

But it was working.

By the time Two was halfway to the surface Scott and Four was just clearing the sludge. As soon as the sub was completely clear Virgil started retracting the claw while Alan sped up his retrieval too.

Two broke the surface just as Four was brought as close as possible. Virgil was all ready for the swim out, and with Penny's assistance they managed to get Four and the canister on board the module. Virgil locked her in place before boarding.

'We have Four and the canister locked on board. I'm entering her now,' he said, keeping everyone in the loop. The electronics didn't respond to him and he had to manually open the doors.

Heart in his mouth the entire time, Virgil rushed into the cockpit of the little sub. Scott was slumped over the side of the chair, and he cursed. His brother wasn't wearing a helmet. He fumbled at the collar.

'Guys, Scott's not breathing! Penny! I need you!'