In the upcoming episode 15, titled "Fidelis Ad Mortem," of the eighth season of "Castle," Kate Beckett and her team go back to the New York Police Department Academy to investigate the murder of a recruit.

The official synopsis from The Futon Critic reads: "When a recruit officer at the NYPD Academy is killed, Beckett and the team go back to their old training ground to investigate. Meanwhile, Castle must reckon with a decision with profound consequences for him and Beckett."

The recently released 36-second promo trailer shows Kate Beckett using every trick in the book to identify and catch the suspect among the fourteen recruits at the NYPD Academy who allegedly murdered their fellow recruit.

Meanwhile, here is a rundown of the previous episode, titled "The G.D.S."

Castle, Haley, and Alexis flew to Hollywood to look into the memory he recalled when he was missing. When they were checking in the hotel, an envelope addressed to Castle was given to him. It was an invitation from "The Greatest Detective Society" to solve a murder.

When they arrived in the scene, the detective who showed up was Kurt Alexander. It turns out the murdered victim was a local private investigator. Across the country, in New York, Ryan looks into the case that Kurt called him for.

It turns out Haley met Castle over a year ago and the latter ended up not remembering it. Haley went on with her confession which includes knowing Castle's father Jackson Hunt, who asked her to watch over Castle.

Haley told Castle that before he went rogue from the CIA, he asked someone to erase his memory. She added that trying to recall his memory might "unleash hell." So Castle let it go and focused back on the case. It was revealed that the murderer was Trevor.

Castle and the team left Hollywood after the solving the case. Then, Castle begged Haley for another clue about his past. He discovered that he knew about LokSat but chose to erase his memory about it to protect Beckett.

"Castle" season 8 airs every Monday at 8 p.m. on ABC.