The Season 6 finale of "Castle," entitled "For Better or Worse," deals with unforeseen complications on the eve of Castle and Beckett's wedding. It is written by Terri Miller and Andrew W. Marlowe and is directed by John Terlesky.
The episode first aired on May 12, 2014.
Senator William Bracken has finally been arrested for corruption and the murder of Johanna Beckett, Kate Beckett's beloved mother. With her family avenged and a light caseload, Beckett can focus more on her upcoming wedding to Castle. However, a trip to the local courthouse reveals that Beckett has been unknowingly married for the last 15 years to her ne'er-do-well college sweetheart (Eddie McClintock of "Warehouse 13") ever since a Vegas escapade.
Rogan O'Leary, however, proves not only difficult to track but less than willing to sign divorce papers without a few absurd favors from Beckett, including stealing a garage door opener from his ex-girlfriend. Things are further complicated when the predetermined wedding venue burns down.
Just when everything seems to have wrapped up neatly and Beckett is at the altar, the show ends on a surprise twist when Castle's car, with Castle inside, bursts into flames. Castle is nowhere to be found, and Beckett assumes the worst.