One reason Captain Fowler recruits Beckett for the undercover assignment is because she speaks fluent Russian. Stana Katic actually is multilingual and, although Russian isn't one of them, is fluent in five foreign languages.
Stana did almost all of her own stunts for the water torture scenes and was excited to do so.
Meg Cionni later had a supporting role in The Rendezvous (2016), in which Stana Katic plays the lead character. The film also features Darby Stanchfield, who appeared in two episodes as Castle's ex-wife, and Alexis' mother, Meredith.