Alright, Castle fans, see if you can solve this one: The official title for Season 4, Episode 20 is "The Limey."
A quick Google search has helped us identify that "The Limey" was 1999 crime film by Steven Soderbergh about "an extremely volatile and dangerous Englishman [who] goes to Los Angeles to find the man he considers responsible for his daughter's death."
The word Limey, according our bible (MerriamWebster.com, naturally), is slang for a British sailor or more generally, an Englishman.
Any theories for what this episode might be about, detectives in training? Tell us in the comments below!