"Sit down and tell me what you need, please" Sherlock said in a very businesslike tone. That's what he did for a living, so the tone made sense.
"I need to see Arthur Dent. I think you call him John Watson, even if I don't really have idea why. I've seen pictures of you two together, and I think that he might be here with you"
"Dr. Watson is an army doctor. He is not on duty now, so he has a job in a clinic nearby. Contact him, but I don't see why you keep calling him Arthur Dent"
"That's his name. You see, he is my soulmate. There was a weird accident during our intergalactic trip and I ended up here. Then I saw the pictures and I came here" Fenchurch showed Sherlock the pictures that were all over the media. He thought she was completely crazy. He considered telling John to stop his blog for a while, because they were getting a lot of attention and insane people like this woman would show up more frequently.
Sherlock was about to make Fenchurch leave, when John opened the door. Her face was illuminated by something like extreme happiness. Her eyes sparkled and before anyone could do anything, she jumped from the chair and kissed John. She hugged him and wouldn't let go, and John didn't react, he was plainly confused.
John didn't move. Sherlock was bewildered, and an awkward silence took over the room.
"This woman, Fenchurch, claims that you are her soul mate and that your real name is Arthur Dent. Do you have an explanation for this, John?" Sherlock really hoped he did.
"I had never seen her before" he said and the funny woman began to cry uncontrollably. She sobbed and said a lot of things that neither John nor Sherlock could understand. She spoke about flying and the dolphins and the end of the planet and a lot of things that didn't make sense at all.
They left her crying in the living room and they went to the kitchen. Sherlock had never seen someone jump from one extreme of the range of possible human emotions to the other in such a short period of time. He was confused. She seemed to be authentic in her manners, he couldn't detect lies on her voice or expressions, and yet every single thing she said was impossible to believe.
John gave her a cup of tea. "This will restore my normality" she said, and she started crying again. So there they stayed, waiting for her to calm down. Sherlock was extremely annoyed, but he was curious because he couldn't detect what was wrong with the whole situation.
Then she opened her small purse, and she showed them a picture. It was one of those instant pictures, those that come out of the camera as a milky square and slowly show themselves. The picture showed her and John in London, they were both smiling and looking like a happy couple.
"This is us, Arthur" she said, looking deep into John's eyes. Now she was serious and had complete control of herself.
Now Sherlock was confused because he couldn't find any sign that the picture was a fake or any evidence of modifications. He examined it and found nothing wrong with it. His mind was working at full capacity, trying to find a logical explanation for this.