The Greek interpreter-SPOILER

It was all pretty well explained in the episode, but here goes. She had a lot of money but the brother was the trustee of her fortune. Which he was apparently going to sign over to her on her wedding day, had it been a normal marriage (and according to custom) instead of two foreigners trying to use her to scam the money. So they were torturing him to try and force him into signing over the money. It's a little different in the short story though, she's not really as cold-hearted. The story basically ends after finding the two men (the prisoner and interpreter) in the abandoned house, all the stuff on the train was created solely for the television version. So they actually get away from Holmes taking the girl with them. But I'm thinking Katrides didn't sign over the money, I could be wrong about that though. It's only later, through reports, that Holmes and Watson learn that the two men have been stabbed to death in Hungary. The police believe that they killed each other in a fight but Holmes believes she killed them as revenge for her brother.

I really like what they did with that episode, it's one of my favorites. I think the stuff on the train was great and the ending much more satisfying than the short story's ending.

"Dan Marino should die of gonorrhea and rot in hell. Would you like a cookie son?"