A/N: Inspired by a prompt from cirquedusoleil19.

Molly Hooper mentally thanked the concierge at their hotel for telling them about the Crystal Cave. It promised to be full of interesting stalactites, stalagmites, limestone formations, and crystals of all sizes. Thankfully, the paths were clearly marked and the cave system was well lit. Still, another natural wonder caught her eye.

There's just something about a nice arse in tight denim, she thought, smirking, as she followed her boyfriend deeper into the caves. Of course, his is genetically modified to be the perfect arse, which makes the view even better.

Said boyfriend – Khan Noonien Singh, former war criminal, former would-be conqueror of the world – chuckled as he climbed over a waist-high boulder. "Shouldn't your eyes be on the path ahead of you instead of my arse, Molly?"

She grinned. "Well, it is ahead of me, and I intend to take a hands-on approach to exploring it when we get back to our hotel room."

"Whatever happened to the timid woman I met when I first landed in this century?"

Khan had stolen a shuttle from the Enterprise and ended up in an alternate 21st Century London than the one he knew via a wormhole, which had immediately collapsed as soon as he went through it. Effectively trapped, he was quickly brought to the attention of Mycroft (crashing a 23rd Century spaceship in the center of Stonehenge was certainly enough to do it), who decided such a man needed to be locked up, for everyone's safety.

Once Sherlock had heard what happened, he insisted on assessing Khan himself and brought John and Molly with him. While Sherlock was fascinated with Khan's genetics and engineering skills, Molly was fascinated by the man himself and was determined to give him a second chance at life.

"She was emboldened by the romantic attention she received from the cocky man you were."

Khan turned to grin at her, a grin that was decidedly still cocky, then turned back to the path just in time to smack his forehead on a low-hanging stalactite. He immediately raised a hand to his head, his steps staggering.

"Khan!" She helped him over to a small boulder and insisted that he sit down. When he removed his hand, she could see he was bleeding from a small gash on his forehead. "And you teased me about bringing a first aid kid," she said, smiling a bit, as she started taking things out of her fanny pack.

He smiled weakly. "I was teasing you about the fanny pack, not what's inside it."

"How's your vision?" she asked as she stood between his legs to clean the wound.

"Currently filled by the loveliest sight in the cosmos."

Molly smirked. "Flattery won't get you anywhere with me, Mister." She bandaged the wound then took his hands and pulled him to his feet. "We should go back."

"A head injury is not the ending I had planned for this outing," Khan muttered, not meeting her eyes.

She raised an eyebrow. "Oh?"

He pulled something small out of his pocket then got down on one knee before her. Molly almost couldn't hear him over the blood rushing in her ears.

"Molly … you're the first person in my life to ever believe that I could be a good man. For that, you have my undying loyalty." He reached out to take her left hand. "You give me pleasure after a lifetime of pain. That first night together … all I could think about was pleasuring you and how much pleasure you were giving me. What I forgot to mention is that I'm … I'm completely in love with you. I need you with me always, Molly. Will you marry me?"

Joyful tears fell from her eyes as she beamed at him. "Yes, Khan. And I love you too."

The diamond ring he slipped on her finger outshone all the crystals around them.