It took almost every department operating at peak efficiency for the Sirius to traverse the Underspace smoothly. Stellar science officers had studied the bevy of new findings about conditions inside the corridors, preparing them for what to expect. Engineers, equipped with such warnings, had fine-tuned every system to make ready for the rigours of the journey.

Even now, deep into their expedition, Rourke stood on the bridge and watched as Locke worked alongside Danjuma at the science posts, the astrophysicist just as important as the department head, if not more, in studying every aspect of their journey as it unfolded. Across the cavernous heart-chamber of the ship, Commander Far sat at Ops, Cortez across the other side of the controls to her, adjusting their systems in real-time at every kilometre covered, every shift in the ebbs and flows of tachyon particles.

An alert pinged at Tactical, and Rourke’s heart leapt into his throat until Commander Rhade said, ‘Liberty has shifted slightly out of our slipstream at the last turn.’

‘Got it,’ called Lieutenant Harkon at Helm. ‘Slowing by point-two to let them catch up.’ While the advanced Sagan-class USS Liberty was more than capable of traversing Underspace on its own, Rourke was keen for the two ships to not become separated. Letting Sirius take the lead, ploughing through Underspace’s conditions like an icebreaker, while the Liberty followed in their wake, kept the two ships together.

Shep was still sat in the XO’s chair, chin propped up on her elbow, drumming her fingers on the armrest. ‘We could be anywhere in the galaxy right now if we broke out of the tunnels,’ she mused, ‘and this is kind of boring.’

‘You wouldn’t be saying that,’ piped up Harkon, ‘if you were at the helm.’

‘Then let me have a turn -’

‘Hey, that’s not how it works, Shep -’

‘Enough.’ Rourke didn’t realise how irritable he was until he sank onto the captain’s chair beside his restless XO. ‘We need to focus.’ He knew Shep was trying to fight the tension, but he found the knots in his gut altogether too implacable for that kind of irreverence.

He looked over to Science. ‘Have we picked up the Ihhliae’s trail yet?’

Locke blew out his cheeks. ‘The odd trace of that fainter, more dissipated signal. But nothing serious, sir.’

‘I think we have to consider the possibility,’ said Danjuma anxiously, ‘that we’re detecting the passage of debris.’

Rourke raised a hand. ‘It’s considered. Thank you.’

‘I mean of the Ihhliae. The difference in the plasma emissions we’re detecting of Endeavour’s passing and the Romulan ship’s suggest, well, one ship’s in one piece and the other isn’t, which means Endeavour –’

‘We follow the trail.’ It was too ghoulish for Rourke to seriously contemplate that, in this instance, poor fortune for the Ihhliae suggested good fortune for Endeavour.

The two science officers exchanged a look, and after a beat, Locke seemed to realise it fell to him to speak. ‘The trail, sir, suggests an exit point up ahead, and Endeavour’s departure from Underspace.’

Rourke sat up. ‘How far?’

‘Twenty minutes at current speed.’

They waited. Or, rather, Rourke waited, hands claw-like on his armrests, while the officers around him remained entrenched in their journey. For them, it was like walking on their hands across a tight-rope. For him, it was the churning agony of sitting still and doing nothing.

‘Aperture detected -’

‘Signalling our exit to the Liberty –’

‘Slowing to point-four -’

‘Navigational deflectors at full -’

The deck rumbled but did not buck. Rourke was still too new to the Sirius to know her every shudder and quake, and worried a little she was so mighty he would perhaps struggle to recognise her milder warning signs. But no alert sirens went off, and with nothing more than the sense of scraping the edges of subspace, the viewscreen cleared for the bronze maelstrom of Underspace to fade, and the darkness of deep space to rush back up before them. It was as if distant stars were suddenly going to shatter the front of the hull, and he braced – then nothing.

All was irrationally silent for a moment as his officers stopped and read and metaphorically checked for ten fingers and ten toes.

‘Liberty is off our aft. They report a smooth transition,’ Rhade confirmed.

‘Still confirming our position,’ called Harkon. ‘But initial scans suggest deep Delta Quadrant, sir.’

‘We’re inside a star system, K-class star,’ said Locke, hands dancing over his controls. Rourke couldn’t help but think of the effortless grace with which Airex absorbed and relayed a billion facts, while Locke was a little slower, a little more thoughtful. ‘Picking up an O-class planet nearby, third in the system.’

Rourke stood. ‘Any sign of our ship?’

‘Sweeping for Starfleet signatures,’ Rhade said.

There was a hushed, ‘oh,’ from the Operations controls, and Rourke’s head snapped around, ready to bark at the occasionally timid Far for burying the lede on something that had shocked her.

But it wasn’t Far. It was Cortez, turning on her chair towards him. ‘No signatures. But there’s metal debris in orbit of that O-class. Duranium alloy and component remains matching Starfleet construction.’

Rourke considered asking if she was sure; duranium was not uncommon. But this was Cortez. She wouldn’t have said if she weren’t. ‘Mass?’

‘Tiny. Could be part of the ship. I need to scan a little more first.’

He turned back to science. ‘Possibility Endeavour had a shaky escape from Underspace, broke up on exit and crashed on the planet?’

Locke winced, though looked relieved that he didn’t have to voice that option first. ‘Feasible. We’d need more scans; the initial sweep suggests significant heavy water composition on the planet, which is going to make picking out any possible wreckage of Endeavour even harder on a planet we… don’t know anything about.’

Shep was on her feet beside Rourke, and dropped her voice. ‘There are a billion options here,’ she noted. ‘A big-ass planet they could easily have gotten lost on. Or maybe they pushed on somewhere else. Or turned around and went back in to Underspace. Isa might have nothing more than a chunk of errant hull plating.’

He worked his jaw, but nodded. ‘How sure are you, Commander Locke, that Endeavour exited Underspace here?’

‘Uh. Let’s say seventy per cent.’ At Rourke’s sharp look, he shrugged. ‘Sorry, sir. The trail didn’t end here directly. But that could be traces of plasma carried along on the particle flows. Or they exited and re-entered.’

‘But there is a trail that carries on through Underspace.’

‘There is what might be a trail carrying on through Underspace.’

He scowled and jabbed a finger at Cortez. ‘Figure out what that debris is.’

‘Sir!’ Rhade’s voice was sharper, the most concerned anyone had sounded since they arrived. ‘Sir, we’re not alone out here. There’s another ship, in orbit of the fourth planet’s moon.’

Rourke made a sound of frustration. ‘Don’t tell me we’ve got some locals. Signal Ambassador Hale to the bridge -’

‘Not locals.’ Rhade’s eyes snapped up. ‘This is a Ghemor-class warship, sir. Cardassians. I don’t know if they didn’t spot us, or were trying to stay out of sight.’

‘Then let’s be neighbourly. Hail them.’

The viewscreen shifted quickly, banishing the depths of this star system and its mysterious ocean world to show the bridge of a sleek, modern, dimly-lit Cardassian warship. The gul before them was a husky figure, strong-jawed and bright-eyed, but the expression of cautious suspicion could not be denied.

‘This is Gul Kaled of the CUV Edorasc of the Cardassian Union. State your business, Starfleet.’

It was a big galaxy, Rourke reminded himself, and Underspace stretched everywhere. There were a myriad of reasons for any number of people to wander as far as they pleased, without deserving suspicion. He cleared his throat. ‘Commodore Rourke, USS Sirius. One of our ships went missing through these subspace corridors. We’re on a rescue mission.’

‘We have seen no ship.’

‘Can I ask your business?’

‘We are on assignment for the Union, Starfleet. Continue your work and we’ll continue ours.’

Out of the corner of his eye, Rourke realised Locke was gesticulating a little wildly. He frowned at the viewscreen. ‘A moment, Edorasc.’ He gestured for the channel to be muted, and turned sharply. ‘What is it, Commander?’

‘I know him,’ Locke hissed, even though he couldn’t be overheard. ‘Kaled. We worked together on Avalon.’

‘Huh.’ That was useful. Rourke pursed his lips, then ushered Locke over. ‘You talk to him, then.’

‘Oh, I didn’t mean we’re friends…’ But Locke stumbled over anyway, and the moment he appeared within sight of the viewscreen, a glint of surprise did enter Kaled’s expression. ‘Ah, hello, Gul.’

Rourke resisted the urge to smack his forehead at the stumbling greeting.

But Kaled inclined his head. ‘Commander Locke. This is a surprise.’

‘The same to you. Congratulations on your own command.’

‘And congratulations to you, Commander, on a more prestigious posting than a research think-tank.’

‘I…’ Locke looked like he might defend his past work, then cleared his throat. ‘We really are on a rescue mission. The ship went missing five days ago. It could have arrived here as recently as 110 hours ago. I get that you’re here on important Union business, but I promise you, we’ve no interest in your mission. If we knew when you arrived, that gives us a window…’

‘Fifty-three hours.’ Kaled looked rather long-suffering. ‘It is entirely possible your ship was here. They could be far away by now, by warp or by the subspace tunnels. Or scattered across this star system, and we wouldn’t know.’

Locke clasped his hands together. ‘Thank you. Sincerely.’ He hesitated for a moment, then glanced at Rourke, and stepped back.

Kaled stiffened at this surrendering of the stage, eyes on Rourke. ‘Know the Union will brook no interference with our operations. Good hunting on finding your missing ship. Edorasc out.’

The moment the viewscreen went blank, Rourke turned to Rhade. ‘What are they doing?’

‘There are significant uridium deposits in that moon,’ said Rhade, expression flat. ‘It was hard enough to pick them up on sensors.’

Rourke nodded and glanced at Locke. ‘Who is this guy?’

‘He was the Cardassian liaison to my research team at Avalon,’ said Locke, his brow furrowed with confused thoughtfulness. ‘I always assumed he’d ended up there because he’d annoyed the wrong people. But here he is now, commanding a Ghemor, no less.’

‘Central Command’s a lot more powerful than it was six months ago,’ Rourke rumbled. ‘Maybe he doesn’t belong in the hinterlands so much in this new, militarised age.’

‘I’m not sure he’s a hawk.’ Locke stared at the viewscreen as he mused. ‘A patriot, yes. I’m not sure. He always kept his cards close to his chest with me. I think he thought expressing criticism of the Union might come across as weakness, but he still didn’t quite walk the party line as much as he might.’

‘Regardless, he’s here, he’s doing something for the Union, and we have a window of nearly three days where Endeavour could have been here without the Edorasc noticing them.’ Rourke set his hands on his hips. ‘You say there’s still a possible trail to follow through Underspace?’

‘There’s something. I couldn’t promise you what it is,’ Locke admitted.

‘And every moment, that trail is degrading.’

‘Yes.’

Rourke scratched his beard, jaw tight as he pondered. ‘Alright,’ he said at last. ‘Hail the Liberty.’

Moments later, the figure of the ageing workhorse, Captain Daragon, filled the viewscreen. ‘If this is where the trail leads, sir, then Endeavour’s gone to ground.’

‘Maybe they met their end here. Maybe they set off at warp. Maybe they turned right back around into Underspace.’ Rourke paused and clicked his tongue. ‘There are leads here. Wreckage. This ocean world. A possible search further into deep space. Sirius should stay here and investigate those.’

‘Not to mention,’ mused Daragon, ‘the Cardassians.’

‘Quite. You’re to take the Liberty back into Underspace, Captain, and chase that trail before it goes cold. It might just be remnants of plasma carried along on the eddies…’

‘Or Endeavour’s nowhere near here, and returned to the tunnels.’ Daragon nodded. ‘We’ll chase the trail til it goes cold, or we find them.’

‘Good man. Return here with whatever you find. If we have to leave the area, we’ll drop a buoy with instructions.’

‘Leave it encoded,’ said Daragon darkly. ‘Who knows who’s listening. Understood, sir. Good hunting. Liberty out.’

Cortez had stood up, and approached him the moment the comms went dead. ‘Sir, permission to join the Liberty on their hunt.’

Rourke frowned. ‘You don’t want to rake over the evidence here?’

She hesitated, and dropped her voice. ‘You know as well as I do that if Endeavour didn’t go back into Underspace, she’s probably a wreck on the bottom of that ocean.’ There were other possibilities, Rourke reflected – but they all needed a reason for Valance to take her ship at warp away from the aperture. They had not yet seen any reason for that. ‘Liberty has the best chance of finding them alive, and I know Endeavour’s systems better than anyone. If they’re going to be chasing a weaker and weaker trail through Underspace…’

‘Alright.’ Rourke’s chest tightened. He disliked the idea of splitting up those who cared as deeply as him, even if, in practice, it put someone who would fight tooth and nail for Endeavour on the Liberty. ‘Grab your gear and beam over ASAP.’

‘Thanks.’ Cortez hesitated. ‘Besides. You know as well as I do that you can’t just worry about hunting for Endeavour, now.’ She jerked her head towards the viewscreen. ‘You can’t not try to find out what the Cardassians are up to.’

He made a face and reached to clasp her shoulder. ‘Go find them.’

Cortez left, and Rourke stood for a moment, chewing his lower lip. She hadn’t said anything that wasn’t true. However much he wanted to keep Endeavour as his priority, the presence of the Edorasc was a concern that couldn’t be overlooked. This was no science ship.

He padded back over to Locke, hands on his hips. ‘You say you worked with Kaled, but you weren’t very close.’

‘That’s right.’

‘Half your old team’s now on Sirius. Did any of them get on with him better?’

There was a pause, then Locke’s brow furrowed, troubled. ‘Believe it or not, sir,’ he said carefully, ‘there is someone.’