The next episode of ABC's Castle will finally provide some answers in regard to what happened to Castle (Nathan Fillion) after he vanished.

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Episode 20 of the current season of Castle is titled Sleeper and should finally reveal all the details of what went down when Castle vanished on the day of his wedding. The ABC series released a promo for the episode, with some of the same footage already seen mixed in with a new scene of Castle recalling the experience.

"Last year, Richard Castle disappeared," the promo's voiceover says. "It's time to find out what really happened."

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Castle wistfully explains the experience to someone offscreen (probably Beckett) in the promo.

"Not a day goes by I don't wonder where I was or what I did," Castle admits.

Fillion's costar Seamus Dever, who plays Det. Kevin Ryan on the series, spoke with TVLine recently about this episode and how it would tie into Ryan and Esposito's (Jon Huertas) conflicting feelings on the vanishing.

"What's cool about that is Espo has always been in the camp of 'I don't believe his story,' while Ryan always been [more open-minded]," Dever explained of episode 20. "It's fun to play that balance of, 'Oh my God, is he lying? Is it the truth? How could he do this to us?' Or believing him."

Dever also confirmed that there will be some "finality" to the story while still leaving some things open-ended in case the writers wish to revisit it in the future.

Castle airs Mondays at 10 p.m. ET/PT on ABC.

Watch the promo for the next episode of Castle here:

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Castle, Television, ABC