Richard Castle (Nathan Fillion) is having mysterious dreams on the next episode of ABC's Castle.

Rick Recalls His Vanishing In New Clip From 'Castle'

ABC has released a plot synopsis for the next episode of Castle, which is titled Sleeper. The episode will finally confront what went down during the months that Castle went missing.

"A mysterious recurring dream drives Castle and Beckett to seek answers about the two-month period when he went missing," the synopsis reads. "But their search for the truth has deadly consequences."

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The guest cast for this episode includes Mackenzie Astin as Phillip Bartlett, Michael Dorn as Dr. Carter Burke, Matt Letscher as Jenkins and Maya Stojan as Tory Ellis.

The Sleeper episode of Castle is slated to air on Monday, April 20 in the regular timeslot.

Co-star Seamus Dever, who plays Det. Kevin Ryan on Castle, spoke about this upcoming episode with TVLine, revealing how the vanishing storyline relates to his character and Esposito (Jon Huertas) as well.

"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 back in late March. "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."

He said that this storyline would also have some "finality" to it, while also leaving things open-ended to potentially be explored in the future.

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

Watch the promo for the next episode of Castle here:

Tags: Castle television ABC