Rick Castle has a horrible bought of writer's block after killing off Derrick Storm, the popular main character from his series of best selling murder mystery novels. But as his diva mother drives him crazy and his teenaged daughter attempts to console him, it's a series of real life murders being copied from his books and NYPC homicide detective Kate Beckett that get his creative juices flowing again. After Castle helps the NYPD catch the real killer, Beckett turns him down flat when he offers that they "debrief" one another. Finding himself smitten by the tough as nails detective, he decides to shadow Beckett on her cases as, much to her dismay, she is the inspiration for his new series of mystery novels. As they work together to solve murders, Kate shares the story of her own mother's unsolved murder with Castle. As the two become friends, he decides to look into the cold case in the hopes of giving her closure. But when he offers to work on it with her, he's shocked when Beckett tells him to stay away from her mom's case or they're over. Unfortunately for him, he's found a key piece of evidence that could solve the case. Will he risk their relationship by telling her or keep the truth to himself?