When Castle and Martha are taken hostage by a crew of bank robbers dressed in hospital scrubs and using classic television doctor names, Beckett finds herself on the outside, desperately trying to rescue them -- which proves to be even more difficult with a by-the-book hostage negotiator watching her every move. Castle becomes the de facto leader of the hostages and discovers that the robbery is actually a skillfully orchestrated distraction for an even more sinister plan. But with Castle stuck on the inside and Beckett on the outside, will either be able to foil the bank robbers' plans before it is too late?