Disclaimer: I own nothing of Sherlock BBC.
WARNING: CONTAIN SPOILERS!
"What do you need?"
"If I was not everything that you think I am, everything that I think I am, would you still want to help me?"
"What do you need?"
"You."
It was déjà vu for Molly as she recalled the conversation she had with Sherlock years ago. The pathologist could remember how sad he looked but now those eyes contained more than just sadness; there was also a trace of desperation found in them. It would be dangerous but since when was any of Sherlock's plans not dangerous? She would have to look out for him so he would not fall off the cliff, metaphorically speaking.
"Thank you, Molly. For taking part in this, for taking care of Rosie, for not blaming me…" The pair seated themselves on the gurney and their shoulders occasionally bumped into each other's as the ambulance made its way to the destination. "I know John's opinion matters the most to you but I don't think you killed Mary. She made a choice to take the bullet that was clearly meant for you. Mary knew that she would probably die as a result but she still did it anyway."
The vehicle was at the round-about and Sherlock's shoulder touched hers again. When he spoke, his voice was rough and his tone harsh, "It does not change the fact that she died because of me. Mary gave up her life in exchange for mine. I don't know what to do to make her sacrifice a worthy one." Molly looked at the consulting detective and at that moment, he resembled a confused child. "Save John and live well."
Lost, Sherlock looked at her, "I don't…I don't know if I can do it, Molly, if I can save John. What if I failed?" The pathologist turned and hugged him tightly. His stubble stung her but his words even more so. "Listen to me, Sherlock Holmes. You will save John Watson and after that, you will be the best godfather that you can ever be to Rosie. You understand me?" The consulting detective nodded slowly and she released him from her embrace.
"You're wrong, you know. Your opinion matters to me too. It matters a lot. I just hope that I would never disappoint you, never let you down and if I did, you would give me a chance to redeem myself." Molly did not believe that her love for Sherlock would ever diminish, it would always be there. The nature of her love for him was pure, simple and unconditional. "Be careful, that's all I ask of you, Sherlock."
"John's right. You are the one who learned to see through my bullshit long ago but he's also wrong because you are not the last person that I would think of. In fact, you are the first." The vehicle stopped and trying to clear the air thickening with emotions that he was not prepared to deal with, Sherlock asked as the doors were opened by the paramedics, "Well, are you ready to get the show started, Molly?" The pathologist stood up and sat on the floor of the ambulance while he laid down on the gurney, "Ready."
Author's note: My version of what might took place inside the ambulance :)