“Deep Cover” offers an unusual murder of a record store clerk who had recently returned to his hacker past before being killed in Coney Island and returned to his apartment. After Tory Ellis (Maya Stojan) breaks the hacker’s encrypted laptop, the trail leads Castle (Nathan Fillion) and Beckett (Stana Katic) to an international monetary organization run by none other than Castle’s spy father (James Brolin) who takes steps to prevent Castle from revealing his true identity to Beckett.
After he becomes Beckett’s prime suspect in the murder all evidence of his latest cover identity “Anderson Cross” is immediately erased, his offices are closed down, and Castle’s father completely disappears. Once Beckett makes the connection to the sketch of the unknown man involved in Alexis‘ (Molly C. Quinn) abduction things become increasingly complicated (and aren’t helped by the wounded spy showing up on Castle’s front door in need of emergency surgery after getting shot) which leads Castle to go to Martha (Susan Sullivan) for advice and come clean to Kate about the true identity of her murder suspect.
As expected, the truth behind the murder of the hacker and the involvement of Castle’s father is far more complicated than it initially appeared as the wounded spy is forced to sit on the sidelines and rely on Castle and Beckett to stop the killer, who is actually a mole (Rick Peters) planning to sell a list of the CIA’s undercover operatives abroad to Iran. However, when Castle gets in over his head his dear old dad shows up to make the last-second save (even if he does have to use the pair of them as bait teaching the mystery writer a valuable lesson).
Brolin’s return works in many ways as it forces Castle into the uncomfortable position of lying to Beckett and gives Martha long overdue closure with the man who fathered her only child. His return also helps Castle come to grips with the fact that as cool as it is to have a mysterious spy father, the man isn’t family. The episode ends on a nice note with the pair finally setting their wedding date which, if true, means we won’t see Castle and Beckett walk down the aisle until early next season.