"High School Musical" star Corbin Bleu guest stars in Season 8, Episode 9 of "Castle," in which the crew investigates the death of a high school a capella singer.

Movie News Guide reports the episode, titled "Tone Deaf," marks the show's return for the second half of the season. It also kicks off three episodes over the next seven days, including a special Valentine's Day airing.

The episode on Feb. 8 also highlights the reunion of protagonists Rick (Nathan Fillion) and Beckett (Stana Katic), after they patched up their estranged marriage. The level of "friskiness" between the two detectives reaches an all-time high.

Meanwhile, Rick's daughter Alexis (Molly Quinn) proves instrumental in helping to solve the mysterious murder of the student, whose body is found in the theater of Martha's (Susan Sullivan) show.

TV Line reports in the next episode, entitled "Witness for the Prosecution," Rick appears in court to testify in a case the couple worked. This is the first time the show will feature a courtroom scene after the detectives solve a case.

That episode is also highlighted by Kate's growing feud with public defender Caleb Brown (Kris Polaha). In Episode 10, Kassie DePaiva, Tuc Watkins and Darlene Vogel will also all debut as new guest characters.

Throughout their time apart, Beckett and Castle continued to work together. Following their reunion, they initially decided to remain separated in the public eye.

When executive producers announced the risky extended plot of their separation, co-showrunner Terence Paul Winter told The Hollywood Reporter of Rick, "He finds a way to worm his way into her cases. What ends up happening is, of course, we get to a place where Castle and Beckett are building theory together, figuring out whose behind whatever the murder of the week is. We get to see little pieces of that electricity we haven't gotten to see for a while now. We get to see them really fighting for this closeness they can't take for granted anymore."