Castle's book agent (Debi Mazar) approaches him with a career-changing opportunity, but accepting it would mean the end of his relationship with Beckett; the corpse of an unidentified woman is in a manhole.
Pete's brother (Kyle Secor) brings their mother (Louise Fletcher) in for a consultation; Violet catches Sheldon asking her archenemy for a date; Cooper treats a young music prodigy who has a brain tumor.