|Appearances|| "Pandora" |
|Portrayed by||Josh Stamberg|
Martin Danberg was a loyal CIA agent working under Sophia Turner, appearing to serve as some kind of right hand man.
Danberg assisted Sophia in bringing Castle and Beckett into their operation to stop a rouge CIA agent, Thomas Gage. He assisted in this operation as best he could and even freed Castle and Beckett from the car trunk Gage locked them in. (Pandora)
Danberg was identified as the rogue agent who had attempted to trigger a cascading political and financial crisis that would bring down the United States, and who had killed Gage to cover up his role in it. Danberg responded by instantly taking another CIA agent hostage at gunpoint and escaping.
However, it turned out that Danberg had been framed by Sophia. He had escaped so that he could trail the real turncoat to identify her and prevent her from starting the crisis.
When Turner revealed her duplicity and was about to kill Castle and Beckett, he appeared and killed Turner instead. With Castle and Beckett's help, he caught her remaining accomplices and foiled the CIA mole's dastardly scheme. (Linchpin)