|Mate Haumann as Kelly, Scott Alexander Young as Hereward Carrington, and
(UPDATE) Luca Bercovici as Dr. Crandon.
The IMDb page for HISTORY's Houdini miniseries has been updated with more cast and characters. Newly listed are Máté Haumann as "Kelly", Scott Alexander Young as "Mr. Carrington", and George Mendel as "Mr. Bird."
I don't know who Kelly might be, but Mr. Carrington and Mr. Bird are almost certainly Hereward Carrington and J. Malcolm Bird. Both were members of the Scientific American committee that investigated Mina Crandon aka Margery the Medium, and both men worked against Houdini as secret informants for the medium. While I assumed the miniseries would feature Margery, this is the first real conformation of that.
It's also my guess that these actors -- who all hail from Eastern Europe -- add their names to the official Houdini IMDb page only after their scenes have been completed. The fact that Young and Mendel's name were added just today tells me they probably recently wrapped the Margery scenes. Might that mean we'll soon learn who's playing the famous medium herself?
Houdini stars Adrien Brody as Houdini and Kristen Connolly as Bess. The 4-hour miniseries is being directed by Uli Edel from a script by Nicholas Meyer. Houdini is an A&E Studios Lionsgate co-production. It will air over the course of two nights on HISTORY in 2014.
UPDATE: You can now add Luca Bercovici as "Dr. Crandon" to the roster. Of course, this would be Margery's husband, Dr. Le Roi Crandon.