"Castle" Season 6 Episode 3, "Need to Know," is back to its original location, the12th precinct and its original team though working, separately. But, the end of episode opens the door wide open for Kate Beckett (Stana Katic) to get back her NYPD badge. The feds have given her the pink-slip.

Castle (Nathan Fillion) has a problem staying in the loft and his name is Pi (Myko Olivier), Alexis' (Molly Quinn) new friend. He soon finds a perfect case to escape the problem -- the murder of a former child star, Charlie Reynolds, who starred in the 90s, high-school sitcom '2Cool for School'. Esposito (Jon Huertas) and Ryan (Seamus Dever) are initially reluctant to let him on the case, fearing that Captain Gates (Penny Johnson Jerald) may not like that. Castle tells them that she won't be returning from a conference soon and that, they can exclusively benefit from his out of the box, crime solving mind.

Charlie Reynolds was found hanging from a hook of a construction crane by a jogger. Initial investigation indicates a struggle and push from the roof of the building. The former-star had an apartment in the building and was sub-letting at another location till the competition of the renovation work. Ryan finds a piece of paper in the dead victim's pocket, which has nine-digit number scribbled on it. The preliminary findings lead Ryan, Esposito and Castle to Reynolds' agent. The agent had called him, threatening to kill him as she believed he is double-crossing her. She tells the trio that she found a deposit of 1 hundred and 25 grand in Reynolds' bank account and wanted to confront him on that.

Captain Gates returns to the 12th precinct earlier than the scheduled date. She objects to Castle getting himself insinuated into the Charlie Reynolds investigation. However, Beckett and McCord (Lisa Edelstein) soon appear to take the case away from NYPD, telling Esposito and Ryan to report all the preliminary investigation to them. Beckett and McCord refuse to divulge any information and why Feds are involved in the case. Later, Beckett learns that McCord also does not have much information on the case and why Feds are looking into it as most of the time they don't have the complete picture.

Esposito and Ryan stop Castle from offering Beckett and McCord the coffee as he had installed the Espresso machine for the NYPD. They tell Castle to find the details from his fiancée to prove that he is not the inside man of the Feds. Initially, Castle refuses to do that but Ryan and Esposito tells him that it is time to pay-up and that his whole relationship with Beckett is based on the foundation of his boundary pushing. Castle prepares a latte for Beckett to get information out of her, but Beckett is smart enough to smell foul-play. She tells Castle that he is bribing her and that he cannot "Castle her."

Despite the Feds taking over the case, Ryan, Esposito and Castle continue working on the case. Dr. Sidney Perlmutter (Arye Gross) tells the trio about the chicken poop stuck on Reynolds' shoes. Castle, Ryan and Esposito meet Reynolds former co-star, Ramon Russo, with whom he had a history of acrimonious relationship. Russo informs the trio that Reynolds and he were working on the sequel of '2Cool for School' and he did appear anxious and tired prior to his murder. He tells them about having a better acting career than Reynolds and that he had no motive to kill Reynolds.

Castle, Esposito and Ryan zero in on the producer of the movie, Hank Harper, as numerous charges of embezzling money have been reported against him. The producer informs them he wouldn't dare siphon-off money as Russians were financing the movie. Apparently, '2Cool to School' was a big hit in Russia. He gives the trio the account book.

Castle, Esposito and Ryan find the nine digits number, which is the invoice number of a consignment containing camera equipment, which was shipped from Russia. The trail of this consignment leads them to a warehouse in Brooklyn, which is close to a chicken processing unit. The trio figure out that the chicken poop on Reynolds' shoes came from there and he must have visited the warehouse. The three reach the warehouse and find out the consignment. Castle, Esposito and Ryan open the box to find guns in it. Beckett and McCord reach the spot and the jogger who first spotted Reynolds' body also appears. The jogger turns out to be CIA agent and he reveals to them that Reynolds was working for the CIA and that he was gathering intel on Ivan Renkov, the head of an organised crime gang. Ivan is a fan of Reynolds' sitcom and thus he had agreed to finance the sequel.

The case is with CIA now and NYPD need not investigate it, further. Captain Gates and her team find that unfair as they feel that it was a murder case and they need to find out who killed Reynolds and catch the murderer. Beckett passes on a USB drive to Castle, clandestinely and which leads Castle, Esposito and Ryan to Svetlana, the niece of Ivan and also an actress in the '2Cool to School' sequel. Svetlana tells that she knew about Reynolds being a spy and that they were in love. She also tells that Reynolds was planning to quit the movie and start afresh.

Svetlana's revelation takes Castle, Esposito and Ryan back to Ramon Russo. He turns out to be the man who pushed Reynolds and killed him as he wanted to get the old fame back. For Ramon, Reynolds quitting the movie project meant it was going back to the non-acting, non-glamorous job.

CIA wants Svetlana to be their new spy and provide intel about her uncle, which Beckett feels is wrong. She spills the information about Svetlana, which saves her from being the spy and also she gets herself the protection and a shift to a new location.

Castle and Beckett are finally spending some time together and Castle shows her the key to his new apartment in Washington D.C. But, that is not required as McCord comes knocking at Castle's door to inform that Feds know that Beckett leaked the information about Svetlana. McCord tells Beckett that she has been fired.