Part 2, Chapters 6-10

[Lou]

I'm betting Mary Debenham had something to do with this. I mean, the next chapter is her interrogation so we'll see but that mysterious man; dark, small, with a womanish voice? That could be her in disguise....
But then would she actually commit the murder? She doesn't seem the type...

[Diana]

This case is perplexing! I feel like Watson right now. All these clues and not sure what to think lol. But yeah, if I had to suspect someone I agree with what you said about Mary Debenham.

[Kelly Rose]

I still don't know if the movie and book have the same ending and I honestly don't remember the details of it anyway so I'm just going to ignore it entirely and focus on the book. I had the exact same thought though about the womanish voice. Especially because the description doesn't fit anyone on the train. Unless that person's not on the train and working with someone who is. But yeah, Mary seems like a dignified and honest person; unless it's just for appearances.