New casting for the upcoming Castle finale suggests that Castle (Nathan Fillion) and Beckett (Stana Katic) might not have the perfect wedding.

New Castle Episode Features Castle & Beckett Battling '70s Mobsters?

Eddie McClintock (Warehouse 13) has been cast to play an intriguing new role in the season 6 finale of Castle, per TVLine. The actor will guest in the final episode For Better or Worse, which is thought to be the big wedding episode for Castle and Beckett.

McClintock will play Rogan O'Leary, a "small town hustler" known for scheming who has a "complicated" past with Beckett, according to the report.

Beckett To Face Off Against Mother's Murderer?

TV Guide suggests that Rogan could be a potential complicating factor in the big wedding, though there are no further details about his "complicated past" with Beckett thus far.

Castle show runner Andrew W. Marlowe previously discussed what he has planned for Castle and Beckett as the wedding draws closer.

"What I'll say is we're trying to present a couple who are in the process of planning a wedding, and things get talked about, and things come up as you get close to the date," Marlowe revealed to Give Me My Remote in March. "We think it would be unfair not to talk about it, not to show it, because it is very much a part of their lives."

Before the big wedding, Castle and Beckett will be solving a few more intriguing cases. The next episode of Castle is titled That '70s Show and features the pair grilling a man connected with a '70s mobster. Episode 21 is titled Law & Boarder, a clever spin on the NBC crime drama Law & Order, and episode 22 is titled Veritas, a Roman word that translates to "truth."

Castle season 6 airs Mondays at 10 p.m. on ABC.

Watch a promo for the next episode of Castle here:

Tags: Castle television ABC