Stardate 1324.5

The electrical hum of the Jeffries Tube on Deck 12 was 'off key'. Scotty was sure of it, however much his tricorder and the ship's computer assured him that all systems were calibrated correctly. It had been 'off key' since their trip beyond the galactic barrier, and it still sounded wrong now, even with most of the Enterprise's systems shut down. The engineer had hoped that the upgrades he'd helped install over the past month would solve the trouble, but as soon as they'd begun to test the engines he'd noticed it was back. Naturally, no-one else even understood that there was a problem, let alone tried to solve it, so – as usual – Scotty was doing the job himself.

Which was why he was lying in the Jeffries Tube with a sonic probe and a phase compensator, trying to track down the source of the errant noise. At least it was quiet on board, he thought – only a few officers and crew were needed for the test run around the solar system, so that made it easier to concentrate on what he was doing.

Carefully, he pried the cover off the main connection array for the gravimetric sensor circuits and switched on the sonic probe, shaking his head as his tricorder assured him, again, that there was nothing wrong with the wretched thing. He replaced the cover, pried off the next one along… and the noise changed. It suddenly sounded normal. He stared at the cover, then at its housing. It couldn't be that simple – could it?

"Mr Scott!"

Startled, he banged his head on the overhead conduit, and dropped the probe, cursing as it slid past his knee and straight on down the Tube's sloped floor to the corridor behind him.

"Sorry, sir." Uhura picked up the instrument from where it had come to rest beside her boot heel. "Didn't mean to make you jump!"

Scotty held onto the grab rail and slid out of the Tube, rubbing his head. "Lieutenant, one of these days you're going to be the death of me!" he said, "What's the problem?"

"The Captain asked to see you in his quarters right away, sir – and you didn't answer the comm. It doesn't seem to be working on this deck."

"That's because I switched it off on this deck. Emergency overrides included."

"You're not supposed to be able to d…" Uhura held up a hand. "Sorry. Dumb remark. I'll cancel the diagnostic when I get back to the Bridge."

He smiled an apology. "I should have let you know – I just didn't think it was that important while we were spiralling round the inner planets!"

"It probably isn't," she said, as they walked to the nearest turbolift, "But you know the Captain!"

"You wanted to see me, sir?"

"Ah, Mr Scott." Kirk looked up from his computer console as Scott entered the room, "Tracked down your gremlin yet?"

"No sir, but I think I'll have it run to ground soon." Scotty refrained from mentioning that he felt he'd been on the verge of making a breakthrough when Kirk's summons had interrupted him – it wouldn't help – and stood with his hands behind his back awaiting the Captain's instructions.

Kirk flicked a glance at his computer screen. "I've asked Mr Spock to continue to double as Head of Science and First Officer for the remainder of our mission," he said.

"Yes, sir." Scotty scrambled to find a way of saying He has a tough act to follow without actually raising the spectre of Gary Mitchell. "I'm sure he'll do an excellent job in both posts."

Kirk's mouth quirked slightly, perhaps in recognition of his engineer's outbreak of tact. "I'm sure he will. The reason I wanted to see you is that Spock was my official second officer. I now need to assign another officer of the line to be third in command." He looked up, and Scott's heart sank. "I'm giving you the job."

"But, sir… I'm an engineer!" Scotty knew his protest would be in vain. Kirk would not understand that, for him, saying he was an engineer was pretty much on a par with saying he breathed in and out.

"An engineer with command school training and years of experience," Kirk pointed out, sitting back in his chair and folding his arms.

"Yes, Captain, but…" Scott sighed, knowing that protest was hopeless. He still remembered the frustration he had felt during his Kobayashi Maru test, when he had had to stand on the Bridge and explain what he wanted the engine room to do, instead of just doing the job himself. He was still convinced that if he'd been allowed to just get down to engineering, they'd have taken out the fifteen Klingon cruisers the computer had sent to finish them.

"Mr Scott." Kirk's tone was firm, and he waved a hand at the computer screen. "Don't blame me – blame your record! Even if I ignored your command decisions on the Enterprise, you've taken the conn on other ships – and as if that weren't enough, you were Officer Commanding at Magellan 3!"

"I was a Junior Grade Lieutenant who didn't have the sense to know he was in over his head!" Scotty realised he'd just snapped at a senior officer, and shook his head. "Sorry, sir. It's… a sore point."

Kirk stared at him for a moment, then leaned forward and squinted at his screen as though to check he had read it correctly. "Magellan 3? Scotty, they gave you a medal and a promotion for that! I was hoping you'd tell me all about it over a drink some time!"

"I'll take the drink, Captain – and I'll take any command assignments you want to throw at me," said Scotty, "But I don't talk about Magellan. Not ever."