Another week, another cast member joins CBS’ Sherlock Holmes pilot Elementary.

And this one reveals why Sherlock, played by Johnny Lee Miller, will head to New York City (where the story is set) in the first place.

Deadline reports that Aidan Quinn will play NYPD Captain Gregson:

Just out of rehab, Holmes now lives in Brooklyn with “sober companion” Joan Watson (Liu) while consulting for the NYPD. Quinn will play NYPD Captain Gregson who worked with Sherlock at Scotland Yard after 9/11 and was so impressed with his work that he has invited him to work as a consultant to the police in New York City. Gregson grew accustomed to Sherlock’s “eccentricities” in the U.K., but knows they won’t necessarily fly in the Big Apple.

What do you think of Gregson accepting Sherlock’s “eccentricities” and having to deal with them as issues in New York City? This isn’t sounding all too convincing just yet.

Last week Lucy Liu was cast as Sherlock’s sidekick Watson.