'Castle' Season 8 Episode 6 Spoilers: Detective Slaughter Returns; Episode 9 Details Reveal Spa Day For Beckett And Hayley

ABC's hit police-procedural drama TV series "Castle" Season 8 returns this week with a brand new episode that will see the return of a familiar face. Meanwhile, details for an upcoming episode were revealed ahead of its premiere date.

Citing the synopsis shared over at The Futon Critic for the episode titled "Cool Boys," it indicates that Frank Castle's exceptional skills will once again be enlisted by Detective Slaughter who returns to solve a high-stakes robbery case.

Despite what is expected of the two, things go awry when a dead body is found and is connected to the robbery crime. The new development puts Slaughter in the hot seat when he is considered to be the number one suspect in the crime. Castle, on his part, will be doubling up his efforts to determine whether his friend is guilty or not.

Meanwhile, a report from Design & Trend drops some spoilers for the Nov. 16 episode titled "The Last Seduction."

According to the publication, Rick and Kate will be joining forces to track a murderous grafter.

Not only that, the new installment will also mark the first wedding anniversary of the estranged couple.

Co-showrunner Terence Paul Winter acknowledged, during an interview, that Rick and Castle's marriage is definitely not in a good standing. Nonetheless, the two will still find a way to celebrate the occasion.

Another spoiler report, this time coming from HNGN.com cited Winter's co-EP, Alexi Hawley, teases that the episode will also find Beckett and Hayley bonding together at a spa. The day-off, however, turns out to be an undercover operation in relation to the case.

A slew of promotional photos shared by the media outlet show the two ladies wrapped in white robes, reading magazines, and having a good time.

"Castle" Season 8 airs every Monday, at 10 p.m. on ABC.