A/N: This is my first song fic. I based it on the song One More Night sung by Alex Goot. Here it goes.

So I cross my heart and I hope to die

That I'll only stay with you one more night

And I know I said it a million times

But I'll only stay with you one more night

Molly knew it was wrong to be in a relationship with Jim Moriarty. It went against everything she knew to be right. She knew she should stop, but the problem was, she just couldn't stop.

She woke up on this particular morning next to Jim. She made the same decision she made every single time. This was it. This was the last time. She would slip out of the flat for what she always said was the last time.

"You are thinking awfully loud, mouse." Jim said.

Molly pulled the sheet up over herself. She averted his gaze. "I thought you were still asleep."

"Very much awake. What are you thinking about?"

"I can't do this again." Molly said.

"Why not? I thought you loved this." Jim replied. He placed a kiss on her shoulder.

"Because it's wrong. I can't keep doing this. Last night was the last time. I'm sorry." Molly said. She stood up and pulled on her clothes.

"It was a good run." Jim replied.

Molly smiled. "Yeah, it was."

"One more parting kiss?" Jim asked.

Molly grabbed Jim's face and snogged him within an inch of his life.

"Goodbye, Molly Hooper."

"Goodbye, James Moriarty."

The whole time Molly was at work, she thought about the way Jim was with her. When they were together, Jim was sweet and she was his whole world. Jim would tell her that she was his only weakness, but not to let on to anyone. But this could not go on. If she gave in to her desires, she would end up doing something even more wrong. For some reason, that didn't seem too bad to her.

She goes back. Molly hesitantly knocked on the door wondering why she was here. As soon as Jim opened the door, Molly was kissing him as if he would disappear at any moment. Jim kept her in his grasp when they pulled apart.

"Not to say I wasn't very pleased with that, but what was that about?"

"Just shut up and kiss me." Molly said.

"As you wish." Jim pulled her inside and pressed her against the door. He initiated a beautiful kiss. Molly held onto his shoulders while he placed delicate kisses on her neck and collarbone.

Morning came and Molly woke up to an empty bed. She sat up worriedly. Clutching the sheet to her chest, she looked around for Jim.

"Don't worry. I was just in the kitchen making breakfast. I know it's your day off." Jim said, carrying the tray over.

Molly smiled nervously. "Thanks."

Jim sat next to her on the bed. "You never explained what last night's outburst of affection was all about. I thought you couldn't do this anymore."

"I can't. I mean, I shouldn't. I'm betraying everyone I know." Molly said.

"You keep doing what's wrong, but you can't stop. I know how that feels. How do you think I became the way I am?" Jim consoled her.

"I don't understand my mind. It is wrong. I know it is, but when I'm with you it feels so right to be there."

"Sometimes what you think is best for yourself is the complete opposite of what you really want." Jim said.

"I love this. Believe me, I do. But I was born an angel. I don't know if I can become a villain type. I can't just flip a switch and lose all my innocence." Molly replied.

"That's where you are wrong, my dear. Everyone has a secret deep down that even they don't always know. Some of your mannerisms show a dark persona. What does Miss Adler always say?"

"The thing about a disguise is that it's always a self-portrait." Molly said.

"Good. What else are you told?"

"The best disguise is the ability to hide in plain sight."

"Exactly. Mousy Molly is a façade you've had all your life. I know that deep down you have a dark, confident, and deliciously devious side." Jim ran his hand up and down her back sending shivers down her spine. "So, tell me what it is you really want. Be honest with me and yourself."

"I. Want. You." Molly gasped.

Jim gave her a Cheshire Cat grin. "Then it is me you shall have."

He kissed her possessively. Molly ran her hands through his hair. In that moment, Molly knew this was where she belonged. She was queen of the criminal web, and she wouldn't rather be anywhere else.

END

A/N: So please let me know what you think. I was nervous about this one since it was so dark and not my usual fluff. Feedback will make me feel better.