It was like everything around me just melted away, slipping out of my field of vision like paint dripping off a canvas. Everything from my hands to the stars disappeared, until all that was left was black. This all happened in seconds, before the darkness was immediately replaced by an image of a 19th century city. An image that moved.

I was standing in a long, narrow street crammed with people, shops, houses, horses and carts. Everywhere I looked there was something new to see: a man flogging fresh fruit and veg from a quaint little stall, an elaborately-dressed woman climbing into a cab and children pressing their faces to bakery windows. I was so overwhelmed it took me a little while to realise that I could also hear the sound of babbling voices, smell the horse manure in the cab stands… and I felt the burly man that ran right into me.

''Move out of the way, Missus!'' he grumbled irritably. ''Don't just stand there gawking like you've never seen the street before!''

Alarmed, I scurried away down a little side street. Leaning against some black wrought iron railings, I continued to scan the crowds on the busy thoroughfare while I attempted to regain my wits. What the hell has happened to me?

People watching was fascinating, and for an undetermined amount of time I simply gazed in wonder at everything around me. A group of young boys were rolling metal hoops with sticks, just like the ones in an old storybook. The clothes were extraordinary – the rich wore smart suits or bustled corset dresses, whilst the poor dressed in sludge-coloured dungarees or plain, simple tops and trousers. If this was some kind of trick, it was certainly an elaborate one.

After finding no indication of how – or why – I got there, I decided I'd better keep moving. There might be a clue elsewhere, or perhaps an authority figure I could get help from. But what would I say? 'I'm terribly sorry to bother you, but I seem to have travelled about 200 years into the past. Could you please tell me what year it is?'

Broad streets, narrow roads, dead ends with crammed terraced housing. The ring was tight around my finger, much tighter than it had seemed earlier. I slipped it off and deep into my coat pocket. On and on I walked, until my feet started to ache and the sun began to sink below the rooftops. Nobody gave me strange looks, or asked why I was wearing pyjamas underneath a coat the likes of which they had never seen. It was as if they looked at me and saw an ordinary teenage girl… ordinary for the century, anyway.

Up ahead I saw a disused factory, towering over the humble dwellings. Red brick walls were streaked in grime and black dust, and a metal staircase leading from the pavement to the top floor door looked rickety with rust. The door itself was open, and a man in an old-fashioned police uniform was walking through it. Tall comedic hat, navy jacket with a thick black belt and shiny gold buttons. He was the first officer I'd seen, and I was getting desperate. I could always pretend to be lost; that way I could hopefully be given somewhere to sleep for the night.

Picking up the pace, I weaved around the bustling crowds while keeping my eyes on the door. The policeman had gone inside, and there were multiple shadows at the windows. People appeared to be talking in a group, and then most of them moved further into the building. Their shadows decreased in size and then suddenly moved downwards and out of sight, as though they had gone down another staircase inside.

By this point I had reached the bottom of the old stairs, and hurriedly ascended them. If the group was breaking up, I needed to get in there before all of them had gone. I certainly didn't want to end up roughing it on benches like the poor waifs I'd seen, with thin body hands and dark-rimmed eyes.

Those steps were sturdier than at first glance, and my thick-souled trainers made no sound upon them. Reaching the summit, I turned sharply to the door, but my feet lost traction and my legs slipped from beneath me. All I got was a brief glimpse inside the factory floor, where two single shadows danced upon the rough-hewn stone that made up the inner walls. In that split second my hands had failed to grab the railing, and the metal impacted above my left ear, promptly rendering me unconscious.

Voices. Very familiar voices.

…come on, let's go… there's nothing unusual here…

…found no clues thus far… everything appears quite normal… she appeared at the opportune moment…

…just an ordinary character… her head will be fine… police will be back soon anyway…

…not a coincidence, Geordi. I believe… help us find it… typical of a Holmes story…

…but an emerald… doesn't look the type…

Just snippets of conversation on the edges of my consciousness. A throbbing pain on the side of my head. Rustling noises, and then silence.

Heavy eyelids dragged open to a plastered ceiling and a grey arm. A long sleeve sloped downwards towards the side of my face, out of my field of vision. Another man stood with his back to me, wearing a brown coat and bowler hat. Whoever owned the arm must have seen my eyes open, as they shifted so their face was closer to me.

Data! Even in my groggy state I recognised him instantly, and my heart sped up. Topaz yellow eyes, unnaturally pale skin, a serene expression. He was looking down at me curiously, as though he was analysing every micrometre of my face. No doubt he was.

''Greetings.''

My body caught up with my brain, and my jaw dropped. I may have dreamed, wished, fantasised, but I never in a million years thought it would ever come true. I wasn't quite that delusional, though I may as well have been for the impact Star Trek had on my life. And here he was.

''You… you… I…'' it was like my vocal cords were paralysed, and I just couldn't get the words out.

''Yes, I am Sherlock Holmes. Do not attempt to rise: I have not yet staunched your injury. You sustained a high velocity blow to your parietal ridge.''

I closed my eyes, trying to summon some coherent thoughts. Am I in the Holodeck? Actually on THE Enterprise!? Can't he see I'm not an ordinary character? And most importantly… how much do I tell him?

Finally, I settled for an ambiguous truth. ''I don't belong here.''

Data's companion turned around and walked over. Geordi looked grave, and a touch irritated at waiting for me to come around. Nevertheless, he looked down at me kindly through his VISOR.

''Don't be frightened. We're here to help. If you tell us your name and where you live we can help get you back home.''

''Willow. My name is Willow. And I live…'' What an impossible question! Should I pretend I'm just a character and let them continue their story? Maybe whatever time-space distortion thingee that brought me here will spit me back out again soon. If I tell them, they'll know there's another world where people think they're nothing but fiction. It would be a huge breach in Starfleet security!

After weighing up my options, I decided I had no choice but to tell the truth. Maybe it was selfish of me, but I couldn't live the rest of my life in a fake world, in the wrong time. I lived in a relatively rural area, and I've never been a big city fan. They could help me get home.

''This is going to sound crazy…'' I started, looking from one man to the other, ''but I'm not from London at all. In fact, I'm not even from this time. I live in the twenty-first century.''

Data's eyebrows creased, and the two Lieutenant Commanders glanced at each other… or at least, I think Geordi did. They both turned to look back at me, so I tried to assume my best truthful, earnest expression.

''Let me get this straight'' Geordi said, holding up a hand. ''You… are from the future?''

''Well, for this time, yes'' I waved my hand vaguely to indicate our surroundings, ''but for your time I'm from the past. You see… I know who you are.''

Data stands up abruptly. ''Dr Watson, do you think this could be another intelligent Holodeck character?''

''Like Moriarty? It's possible, but he was still a Sherlock character that belonged in this story. If she is truly from another time…''

In full-on officer mode, Data ordered ''Please tell us how you came to be here, and what you know about me and my colleague.''

''Well, for a start you're not Sherlock Holmes and Doctor Watson. You're Data and Geordi La Forge from the Enterprise D. This is the Holodeck – one of them anyway – and you're probably solving a Holmes-style mystery. I've no idea how I got here. I heard a noise in my back garden and went to investigate, hence my attire, and I found… something… that magically brought me here. I don't understand it any better than you do… and probably much less.''

''I do not understand.'' Data was scanning my outfit, his trademark confused look on his face. ''You appear to be wearing clothing that is appropriate for this time.''

''Oh!'' I gasp, having my suspicions confirmed. ''I see – that's why you didn't question me about it! I'm wearing pyjamas, Reebok trainers and my black coat. Do I really look normal to you?''

''This appears to be a small piece of a much larger puzzle. It goes much further than a Holodeck malfunction. If you are telling the truth, then there are evidently distortions in the space-time continuum.''

''But that doesn't explain how she knows about us, Data!'' The chief engineer was agitated and frustrated. ''Starfleet didn't exist in the twenty-first century, and we certainly weren't around. How do we know she's telling the truth? She could've got our names and Holodeck knowledge from a computer glitch, and be just another character that's malfunctioning.''

He was viewing me with such suspicion, and I suddenly couldn't bear it. The Geordi I'd watched thousands of times on screen was so amicable, and rarely got annoyed at people unless they'd done something really careless or wrong. My home and my life had been taken away from me, and now two of the characters I had most loved and admired thought I was either a time-wasting glitch or a fake with a personal vendetta, perhaps even a spy.

I felt around the side of my head, and found that Data had pressed a fabric to my wound. It made me want to be sick: anything to do with blood makes me nauseous. But I took a deep breath, held it there with my hand and struggled to my knees. Gentleman that he is, Data gently took my arms and helped pull me upright.

''Okay, I'll prove it. If I'm truly a simulation, I can't walk out of here, can I?'' Without waiting for an answer, I straightened my spine, put my shoulders back, looked them straight in the eyes (or VISOR) alternately, and said in my authoritative voice:

''Computer, arch!''