Now, I was a big fan of Torri. In fact I have to admit that she was the main reason I decided to watch the show.
But Michelle Morgan who plays Fran/Weir in "Ghost in the Machine" does a pretty good job emulating the mannerisms of an established character and because of her performance the whole episode worked.
They also had quite an effective ending where the main characters realise that yes, it was Weir.
I shall keep a look out for Michelle in other TV shows and movies.