"A Chill Goes Through Her Veins" is the episode that first introduces the mythology of the murder of Johanna Beckett, Detective Kate Beckett's mother. Her mother's murder is the reason Beckett became a cop.
Ryan talks of disappearances and suddenly 'you're fighting off Sleestaks on the far side of the dimensional rift'. In the 1970s program 'Land of the Lost' some folks fell through a dimensional rift into a pocket universe where they faced dinosaurs and lizardman Sleestaks.
In this episode of "Castle" the twentieth-century Irish poet, Patrick Kavanagh is referenced by the show's writers. Using the character names of "Sam Kavanagh" and "Detective Raglan", the writers made reference to the poet's 1946 composition, "On Raglan Road". Also of note is the fact that this poem was later set to music by the the Dubliners, (an Irish band), and has since been covered by many Irish and international musicians.