Season 2 premiered on September 21, 2009 with an initial order of 13 episodes. Eventually, it was increased to 22, then to 24.
As Castle prepares for the release of his first Nikki Heat book, he works at mending his damaged relationship with Beckett. Eventually, she forgives him and they resume their regular partnership of solving cases while at the same time flirting and angering each other. However, things get more serious when an obsessed fan of Castle's books threatens Beckett's life and a case reveals a connection to Beckett's mother's murder. Old and new flames also surface to further complicate Beckett's and Castle's feelings for each other.
- Castle apologizes to Beckett for looking into Johanna Beckett's murder case and she forgives him.
- Ryan and Esposito discover Beckett did some modeling in her youth.
- Castle figures out just how much of a fan of his books Beckett is.
- The launch party for Castle's first Nikki Heat book, Heat Wave, takes place around the same time as he has to choose between continuing to shadow Beckett or taking advantage of the opportunity to write a James Bond book.
- Heat Wave sales are so good that Castle's publishing company, Black Pawn, offers him a contract to write several more Nikki Heat books, thereby extending his partnership with Beckett, to her immense chagrin.
- Castle throws a monstrous Halloween party for his friends, including the gang from the 12th precinct, where he dresses as one of his idols, Edgar Allen Poe.
- Alexis volunteers at the precinct for community service hours for her high school.
- Alexis also confides in Beckett for the first time, drawing her father's concern.
- Castle reunites with his former flame, Kyra Blaine, during a murder investigation and sparks threaten to fly.
- The gang catches the man who murdered Beckett's mother who also turns out to be a hitman and part of a larger conspiracy, but Beckett has to kill him before she can discover who hired him.
- Castle gets word that Heat Wave will be made into a movie.
- Beckett becomes jealous when Castle is ranked by a local newspaper as one of New York City's most eligible bachelors.
- Beckett reveals herself to be a baseball fan and has a fangirl moment, when Castle introduces herself to legendary coach Joe Torre.
- The gang finally meets Ryan's longtime girlfriend Jenny, who turns out to be sweet and sincere.
- Castle fears for Beckett's life when an obsessed fan of his targets Beckett, eventually blowing up her apartment. She survives and moves into Castle's loft until the perpetrator is caught. She also is a bit jealous when an accomplished female FBI Profiler fascinates Castle.
- When Castle fears for his life, he makes Beckett promise to take care of Alexis.
- Castle shows he is a fan of Indiana Jones.
- Castle goes on a late night talk show to promote Heat Wave and Beckett grows jealous when he has a fling with an actress who wants to play Nikki Heat in the movie version of the book.
- Beckett meets handsome robbery Detective Tom Demming and strikes up a relationship, causing Castle to take a serious look at his relationship with her.
- Martha gets into a relationship with a man named Chet and eventually moves in with him.
Weird Crime Scenes
Season 2 Intro
Most episodes of Season 2 begin with the following dialogue:
Castle: There are two kinds of folks who sit around thinking about how to kill people: psychopaths and mystery writers. I'm the kind that pays better. 'I'm Rick Castle...Castle...Castle. I really am ruggedly handsome aren't I?' Every writer needs inspiration, and I found mine. Beckett: Detective Kate Beckett...Beckett...Beckett. Nikki Heat? Martha Rodgers: The Character he's basing on you. Castle: And thanks to my friendship with the mayor I get to be on her case. 'I'd be happy to let you spank me.' And together we catch killers. 'We make a pretty good team you know? Like Starsky and Hutch, Turner and Hooch.' Beckett: You do remind me a little of Hooch.