|Before I begin, I have to make some assumptions: 1) This is a finished story, not a rough draft, and, 2) This is a stand-alone story, not a smaller part of a larger tale.
What I Like:
There's a kind of Hitchcock feel to the opening, and a decent amount of suspense during the womens' train escape.
There's a lot of action and dialogue. The pace never lags; you do a good job of keeping things moving.
You set the opening scene well, as far as establishing a main character.
You limited the number of characters, which keeps the reader from getting confused.
Attention to detail, in relation to some of Miranda's actions and reactions, and with the clothing used for the disguise, helps me visualize what's happening.
You put a couple nice twists in the story: one, when Elizabeth realizes she's been drugged, and later, when the conductor foils Cecil's plot.
Suggestions for improvement:
As a rough draft, this would be a good foundation to build a fully fleshed-out story on. But the way it is now, it is too brief. I felt rushed from one scene or place to another, which made it hard to take the story seriously or become engaged in it.
For example, in the beginning, after you've established where Miranda is, Elizaeth rushes in and BOOM, she's suddenly clinging to Miranda. Miranda doesn't ask a single question, and, as if psychic, she somehow fully understands what's going on and hides Elizabeth. In view of the deception Miranda is part of, this would make sense. But as it stands, it is too convenient, not something a normal person would do in that situation. I'd be asking questions- a lot of questions.
Once Cecil leaves the compartment, Elizabeth shares her situation with Miranda, giving a synopsis of her predicament in a few sentences. Not only does it sound scripted, but the fact that Miranda immediately accepts it as the truth- again asking not one single question- stretches credibility to the breaking point. Maybe Miranda is an excellent judge of character, but if I were Elizabeth, I'd be wondering why Miranda is so willing to help a total stranger.
There's a rush to get to the bus stop, a rush to get to London, and then another scripted "speech," where Elizabeth finishes giving Miranda her life story.
Then there's the rush to get to sleep, to wake up, and the rush to see the sights. The story is moving too fast, causing me to lose interest. It feels like the you, the author, are just trying to get the story over with. The rest of this tale feels rushed and compacted, and the ending too pat to believe.
Now, like I said before, the foundation for a fun, interesting story is there. But you should slow down and give your characters some room to do their thing. Sure, Elizabeth is being chased by Cecil, but give her and Miranda time to get acquainted. (Maybe Cecil is a little dense in the tracking department and is taking a while to perform his search.)
Once the two young ladies have decided to work together, then have Cecil appear. And here you could start having fun with the characters. Make Cecil sinister or smarmy. Maybe he has a weird way of speaking or dressing- something to distinguish him from everyone else. After all, he's a villain.
Same goes for Miranda and Elizabeth. They should all be speaking in ways that differentiate them from each other. Miranda is okay, as you have her acting cool and confident. But since Elizabeth is running for her life, you could have her out of breath and speaking in incomplete sentences, just like you would if you were in fear for your life and on the run.
Before I forget, you included a detail here that could make for a very entertaining addition to your tale: with her birthday approaching in less than two days, the clock is ticking. There are a lot of opportunities for Cecil to make attempts on Elizabeth's life. Hitchcock used to do this all the time in his films, and it gave him a chance to ramp up the suspense but also introduce some dark comedy (which is always welcome in stories like this). This would give you the chance to introduce more conflict, especially in Miranda's mind and heart. Maybe she starts feeling bad about Cecil's plot, but to interfere would put her at risk, too.
I am really going on here because I see possibilities for this story- but only if you expand it to do the tale justice. Stick with the structure you've established, but lengthen the conversations, the action scenes, and the suspenseful situations. Those twists in the story can work in your favor, but only if you expand on areas that will give your story the impact you want it to have on the reader.
I hope these comments help, and I'm willing to talk with you further about the story, if you wish. Thanks for sharing it, and thanks for asking me to review it.