As one would have come to expect from their away missions, something just had to go wrong. This time was no different, and Spock and McCoy were trapped by a cave in on a God forsaken mining colony. The minerals were affecting their communications so they couldn't call for help and they had to hope that the sound from the cave in had made enough noise to garner attention. Worse, this section of the mines was previously barricaded due to an inexplicable gas that the miners couldn't tell if it was toxic or safe to breathe.

How they got there was a story in itself that McCoy didn't feel like relating.

At the moment, Spock was doing his best to determine the toxicity of the gas before the last of their air supply from their breathing apparatuses dwindled. McCoy watched expectantly. His eyes widened when Spock pulled off his breathing mask.

"Spock, what the hell are you doing?!"

"The air is non-toxic, Doctor," Spock elaborated. "It would be beneficial for you to take off your breathing apparatus before you choke from the lack of oxygen."

McCoy rolled his eyes and did as he was told. He took a small breathe as if to test the air and then followed it up with a normal breathing pattern. "Well, so we won't die from asphyxiation. But we could still die of starvation in the time it takes the others to find us. Or we'd finally drive each other stir crazy and murder each other-" He shut his mouth immediately. Where the hell did that come from?

Spock quirked his eyebrow as he was prone to do. "Doctor, is that a real worry of yours? You needn't worry. I have no intention of killing you."

"Peachy," McCoy mumbled.

"However, I would like affirmation that you would refrain from killing me."

"I'm a doctor, not a murderer," McCoy snapped in return. He sank against the wall until he was seated on the ground, knees at his chest. "Sorry, Spock, I guess the stress is getting to me."

The Vulcan sat next to him and a look of surprise displayed on both of their faces, though it was less evident on Spock's. "Doctor, I appear to have made a miscalculation on the effects of the gas."

"Oh...?"

"While it is indeed non-toxic, it is not without additional effects..."

"For the love of God- If you weren't so attractive, I'd hit you for stalling." His hand couldn't slap over his mouth any faster.

"Therein is my point," Spock concluded. "The gas appears to make us say, or want to say, exactly what is on our minds."

McCoy stared and risked uncovering his mouth again. "I suppose that 'want to say' line has to do with you being Vulcan and supposedly having better control over your mouth?"

"I would love to show you what control I have over my mouth-." Spock nearly flinched. "As you can tell, I am more immune than you are as human, but not completely."

"Probably because of that human half of yours," McCoy mused, giving up on stopping himself. "Sometimes I wonder if there's any human in you or if you are truly nothing but a Vulcan."

Spock frowned slightly. "I am displeased as always to hear your dissatisfaction for my Vulcan heritage. Do you have a logical explanation for this, or are you merely prejudice without reason as humans are prone to be?"

McCoy gave Spock an affronted look. "It's not that I hate you, Spock, it's that I can't fathom how the hell human and Vulcan DNA can mix to provide an offspring that is physiologically Vulcan. Genetics don't quite work that way on Earth, especially given the different environment, no less different planets, our species evolved on. You've been a mystery ever since I heard about you and I just want to make sure SOME human genes got added to your code."

"...Oh." Spock was silent for a moment, staring straight ahead. "To be fair, you are a mystery to me as well."

"Is that so?"

"I cannot fathom how..." He trailed off, regaining control over whatever he was trying to say.

McCoy was about to insist he continued but was caught off-guard by something snaking around his hand. "What the...?" He looked down and saw Spock gripping onto his hand. "Not quite young school girls, are we, Spock?"

"School girls, Doctor?"

"Never mind. Explain the sudden hand holding?"

"Touching hands is a symbol of intimacy in Vulcan culture."

McCoy glanced over at Spock. "Are you... Kissing me?"

Spock shared the look, stoic and giving no indication of his answer. And then... "By Vulcan standards, yes."

He grinned. "Why, Spock, you sly dog. If you wanted to kiss me, you could have asked."

"May I kiss you?"

"I see no reason to say no, since we're already-." McCoy stopped when he noticed Spock leaning closer to him. Getting the idea, he completed the distance, pressing his lips against Spock's.

He lowered his legs and Spock flipped over to be on top of him. Spock took his hands in his own and continued to kiss him fervently. Once they finally broke apart to give each other a chance to breathe, McCoy smiled up at Spock.

"So, I suppose it's out in the open now about our feelings for each other? Damn gas is good for something, I guess."

Spock got off of him and sat beside him once more. "Indeed. I believe we had an excellent discussion, Doctor."

"Leonard, please."

"Leonard." Spock's hand landed on his again and the two of them sat together in the silence, waiting patiently for something to happen or for one of them to speak or make another move.

"Well," McCoy said at last, "If we die here, at least it will be together."

Spock wasn't given a chance to answer when they heard shouting from the other side of the caved in wall. Someone told them to step back and soon after the wall came tumbling down from phaser fire.

They were soon back on the Enterprise and McCoy examined himself and Spock, monitoring the gas as it left their body. McCoy frowned at the results and glanced up at Spock.

"Strange readings I'm getting here, Mr. Spock."

"Yes, Leonard?"

"According to this, we have normal levels of typical gasses in our bloodstreams with no sign of that mysterious truth telling gas anywhere."

"Fascinating."

"...Spock. I thought Vulcans didn't tell lies?"

"Well." Spock stood up. "As you so pointed out earlier, I am half-human."

Spock nearly fled from the sick bay as McCoy chased him to the door. "Dammit, Spock!" McCoy yelled after him.

He waited a moment and then retreated back inside. At the very least, even if Spock made up the circumstances in order to find out McCoy's feelings, at least those feelings were mutual.

But, dammit, as soon as he got his hands on that Vulcan...