When an ice cream vender is shot, evidence leads Beckett and Castle to believe that an unknown second-grader may have vital information about the case. Castle goes undercover at an elementary school to try and identify the second-grader but nothing goes as planned.
In "Dressed to Kill," a young woman's murder sends Castle and Beckett into the world of cutthroat world of high-end fashion.
"Dreamworld" - Continuing from the season premiere episode, Beckett races against time to find a stolen toxin capable of killing tens of thousands of people. To make matters worse, Castle was exposed, leaving him with less than 24 hours to live.
A murder investigation launches Castle into what seems to be an alternate universe where he's never met Kate Beckett. Castle has to convince Beckett, Esposito and Ryan -- now complete strangers -- to let him participate in their investigation so he can find his way back to his own world.
"Need to Know" - Castle and the boys investigate the murder of former child star Charlie Reynolds. But the case takes a turn for the strange when Agents Beckett and McCord arrive from Washington to take over the investigation.
Castle and Beckett replicate the '70s to solve a murder.
In "A Murder is Forever,"When a famed relationship therapist is murdered, it appears that her access to the secrets of her elite and powerful clients led to her death.
When a body is found in the theater of Martha’s latest show, Castle and Beckett’s investigation leads them into the unexpectedly dangerous world of competitive a capella. “High School Musical”’s Corbin Bleu guest stars.
With their best lead in hand, Castle and Beckett are ready to take on LokSat. But an unforeseen twist puts their case – and their lives – in jeopardy.
Driven to apprehend a killer, Ryan must revisit the events that led up to the shooting, with the help of Castle and Beckett.