Dr. Morgan is replaced by Dr. Vaughn in the episode. Dr. Vaughn is never seen and Dr. Morgan continues to work the case from the shadows. Ioan Gruffudd played Eric Vaughn on an episode of Castle (The Squab and the Quail (2013)).
At the 25:52 mark of the episode there is a brief insert shot of 6th Avenue in New York City. This shot is odd because all of the cars appear to be from the 1990's or earlier thus making the shot atleast 15 years older than the era the episode is meant to take place in (around 2014).