Castle Castle

For ABC's Castle, nothing makes a wedding more memorable than murder.

As Detective Kevin Ryan (Seamus Dever) prepares to tie the knot with his fiancee Jennie (Dever's real-life bride, Juliana) on Monday's episode (10/9c, ABC), the death of a notorious Lothario derails the wedding planning. And things only get worse when Beckett (Stana Katic) and Castle (Nathan Fillion) learn that Jenny has a connection to the womanizing victim.

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"It's sort of an interesting wrinkle," Dever tells "What ends up happening is that everyone else worries about it a little bit more than Ryan does. Beckett and Castle are trying to protect some information from hitting me, and in the end, they sort of underestimate my ability to deal with that information."

But don't expect that reveal to give Ryan cold feet. "It's nice to see one of [the characters] in a stable relationship," Dever says. "I think it's cool because everyone else gets to reflect on what Ryan has. I think it's something that my character owns, which is a nice little space we've carved out for Kevin Ryan."

Indeed, creator Andrew W. Marlowe says that on a show that so heavily relies on its leads' will-they-won't-they sexual tension, it's helpful to have a couple that will. "It's important, not just for the audience, but for the characters in the show to have a touchstone of what they can aim for," Marlowe says. "They need to see something that's functional and happy."

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So, will observing Ryan's wedded bliss help push Castle and Beckett closer toward their own functional, happy relationship? "They're thinking about what it's like to be at another wedding and be single," Dever says. "There's that, 'Why can't we just give into these feelings that everybody knows they both have?' ... Or maybe they'll at least admit some things. Something's got to happen."

Adds Marlowe: "We're looking at characters who are looking for their other halves in life. And they have found each other to a certain extent, but they haven't fully committed to it. So this is part of the journey."

Castle airs Mondays at 10/9c on ABC.