The long wait is over for "Castle" fans as Rick Castle (Nathan Fillion) and Kate Beckett (Stana Katic) returns for more action.

When the show returns next week, fans should expect a cappella scenes in the episode titled, "Tone Death." As stated in the synopsis found in the Futon Critic, Rick and Kate will investigate the case involving a body discovered in the theater where Castle's mother, Martha (Susan Sullivan), performed her latest show.

As the pretend-estranged couple dig deeper to find some answers, they will find themselves in the "unexpectedly dangerous world of competitive a cappella." Since the episode involves music, Corbin Bleu from "High School Musical" will appear as a guest star.

As the midseason premiere approaches, ABC released "Castle's" first-look photos via TVLine. Going through the photos of episode 9, it somehow revealed that Rick and his daughter Alexis (Molly Quinn) found an underground location, presumably where singers converge for a competition, just like how it was in the movie, "Pitch Perfect."

Elsewhere in the episode, fans will also get to see Rick and Kate back together and in bed. In the promo trailer, Kate was seen flirting with her husband and when in public, she was seen punching him in the face.

Meanwhile, the synopsis for episode 10 titled "Witness for the Prosecution" is also available via Futon Critic. "Castle finally gets his day in court when he takes the stand as the key witness to a murder from five months ago. But when new information suddenly arises, he and Beckett must race against the clock to prevent a miscarriage of justice."

This episode will air on Valentine's Day due to the change in schedule explained in a previous report. "Castle" should return to its regular timeslot starting on Feb. 15.

To know more about what's to come in the next two episodes, check out all the photos from TVLine. "Castle" airs Mondays at 10 p.m. EST on ABC.