Last season ended with Beckett wrestling over whether to take a high-profile job in DC -- a dilemma made more complicated when Castle proposed to her. In the Season 6 Premiere of "Castle," Castle and Beckett will deal with the consequences of their decisions against the backdrop of a high-stakes investigation.

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.

With Beckett still in D.C., Castle and the boys investigate the murder of former child star Charlie Reynolds, who rose to fame playing the lovable nerd on an early 90s High School sitcom. But the case takes a turn for the strange when Agents Beckett and McCord arrive from Washington to take over the investigation, creating competitive tension in the precinct. Meanwhile, Castle has to contend with a new face at the 12th, NYPD Detective Frank "Sully" Sullivan.

A desperate young murder suspect, Emma Briggs, takes hostages at gunpoint then mysteriously insists that she will only negotiate with one person: Richard Castle.

A grisly murder investigation leads Castle and Beckett to a suspect who claims he's traveled back in time to stop terrible events from unfolding, events that will change the course of human history. Is he simply a deluded killer, or is it possible that he's telling the truth?

Castle and Beckett investigate the bizarre murder of a young woman who was found ritually posed. When the team finds a collection of strange symbols in her apartment and the prime suspect turns out to be a mysterious monk, Castle becomes convinced they’ve stumbled onto a “Da Vinci Code” style conspiracy. Meanwhile, Castle tries to come to grips with the fact that Alexis and Pi have moved in together.

Alexis enlists Castle’s help on an Innocence Review case to prove that a death row inmate, Frank Henson, was wrongly convicted. With only 72 hours left before his execution, Castle and Alexis (with help from Beckett) urgently investigate the original murder, only to uncover explosive secrets that may seal Frank’s fate.

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. But when Castle and Beckett discover the victim was in possession of a rare object worth millions of dollars, they realize that this case may be even more complicated – and dangerous – than they thought.

When a woman who looks very similar to Lanie is murdered, the team thinks the killer may be targeting members of the 12th precinct.

A man dies inside a church, protecting a baby. The team has to find the guy's killer and the baby's parents. The man is connected to a crime, but his protecting the baby does not fit a criminal character.

Castle and Beckett must find a serial arsonist as Ryan and Esposito struggle for their life in a building set on fire.

Castle and Beckett have to deal with the sudden appearance of Castle's father while solving the murder of a computer hacker who was working for the covert agent.

When a rising young pop star is found dead in an alley, Castle and Beckett delve into the victim's out-of-control hard-partying lifestyle, but as they dig deeper, a shocking revelation threatens to rock their investigation.

The murder of a PA at a top fashion magazine brings Castle and Beckett face to face with a tangled web of suspicion and corporate politics - and with the magazine's formidable editor, who still remembers Beckett's brief career as a model.

Castle and Beckett investigate the death of a mean high school girl at one of Castle's alma maters. Castle is thrilled when he discovers that it might be the work of a teenage telekinetic.

Castle and Beckett are baffled when a confused woman with an unshakable alibi gives a detailed and convincing confession to a murder. Then a second person walks into the precinct and makes the same confession. And then a third.

Investigating the killing of a Japanese ballerina, Castle and Beckett find a shrine with the murder weapon in an old factory. Then, when the two are separated, Castle is ambushed by a hooded attacker bearing all the hallmarks of a ninja.

A man dies inside a church, protecting a baby. The team has to find the guy's killer and the baby's parents. The man is connected to a crime, but his protecting the baby does not fit a criminal character.

Investigating the death of a Wall Street trader leads Castle and Beckett to discover that the victim was an undercover informant for the U.S. Attorney's office.

When construction workers uncover a mobster's body buried in concrete for 35 years, Castle and Beckett must try to talk to a fellow mafioso so stricken with grief that he lives as a recluse in a Seventies time-warp.

A promising professional skateboarder is killed by a motorcyclist, so Castle and Beckett dive into the world of extreme sports to investigate the murder.

Beckett conducts a covert investigation related to her mother's murder but things go terribly wrong when the subject under surveillance is killed. Castle and Beckett become the object of a manhunt when evidence connects Beckett to the victim.

In the sixth-season finale, Castle and Beckett prepare for their wedding. However, an unwelcome surprise may ruin things, so they embark on a zany adventure, encountering masked men and mad bikers along the way.