[This is a review of Castle Season 6, Episode 9. There will be SPOILERS.]

What makes ‘Disciple’ one of the great Castle episodes is that it would have been good even without the links to the beloved/hated 3XK murders. The case plot revolves around two corpses who resemble two members of the 12th precinct team; there are several sharp twists and blind curves along the way, and both of the two possible suspects are deliciously evil. The addition of the 3XK tie-ins just make the experience that much richer.

The opening scene sets the tone for the rest of the episode: dark, mysterious, with a plot twist hiding in plain sight. William Mapother does a superb job playing security guard Carl Matthews. You almost feel bad for the guy, having to chase off homeless men in the middle of the night and then talking to a corpse before realizing she’s swinging from a fishing wire and has been dead for a while.

But as soon as he’s in the interrogation room, a whole new man comes out and the acting talent is ratcheted up a few notches. Forget mister nice guy – this is the predator you fear your kids will one day meet on the internet.

No less talented but oily as a used car salesman from the get-go is Annie Wershing as Dr. Kelly Nieman. Where Matthews didn’t rate a second glance, you knew from the second Castle (Nathan Fillion) and Beckett (Stana Katic) sat down at her desk that she was in it up to her pretty little neck.

You could probably also guess that the pen she seems so eager to foist on Castle would mean something, too, and it wouldn’t be shocking if the same ends up true for the business card she gives Beckett. Still, all they can pin her down for is ordering Daniel Santos’ special services from time to time and working her plastic magic on Pam Hodges.

Equally satisfying is the time granted to the ensemble members of the cast. Those pining for more of Ryan (Seamus Dever), Espo (Jon Huertas), and especially Lanie (Tamala Jones) can have their cake and eat it too this time around.

Lanie and Espo are unnerved enough when their respective doppelgängers turn up dead and that tension only compounds as the killer’s true motives come to light. Given that Ryan and Castle have been targeted by Jerry Tyson (Michael Mosley) in the past and now Lanie and Espo, Gates (Penny Johnson Jerald) and Beckett better watch their backs.

Of course, that worry would only be valid should either Gates or Beckett decide that the murders and evidence theft are a direct result of interference from not-so-late, great Tyson and not merely two sick people paying homage to a dead man.

Neither woman seems ready to jump to that conclusion, nor is the NYPD. Yes, all sights are set on reeling in Dr. Nieman and Matthews will serve his time, but Beckett is finally ready to embrace the lessons Castle taught her throughout the years and stop chasing ghosts in favor of living in the present.

Will she come to regret that decision? Is Tyson dead or alive? Would you prefer Matthews or Nieman on your “accessory to murder” list, or both? And more importantly, do you think Castle’s pitch for a honeymoon in Middle Earth should be revisited?

Castle returns next Monday with, ‘The Good, The Bad & The Baby’ @10pm on ABC.