[This is a review of Castle Season 6, Episode 16. There will be SPOILERS.]

Whether or not it’s meant to set the stage for ABC’s new drama Mind Games – which premieres tomorrow night – tonight’s Castle does do a good job of showing how the human mind can be tampered with. “Room 147″ also sees the return of Alexis (Molly Quinn) and delivers the long-awaited news that Pi (Myko Olivier) is history.

At the start, the case is every bit as bland and boring as Castle (Nathan Fillion) says it is. A man is dead and a woman has confessed to killing him. The problem is, Anita (Alexie Gilmore) was seen by plenty of other people at a restaurant at the time of the murder. Only when two more people step up and confess to the killing as well does the plot become interesting.

What sells the bizarre chain of events is the casting of John Getz as Dr. Gustavo Bauer. Getz has made his fair share of TV guest spots over the last couple of years, in everything from NBC’s Law and Order: SVU to ABC’s NCIS: Los Angeles, and most recently on Fox’s Bones. Here, he’s the perfect man to sell the role of a creepy cult leader guilty of everything but murder.

Also pleasant is the return of Dr. Holloway (Phil LaMarr). The brilliant shrink from a few seasons back is a good fit for the man needed to figure out what is going on with the three would-be murderers. Sure, they could’ve just as easily gotten Lanie (Tamala Jones) to run labs and find a potentially mind-altering drug in the victims, but it would have been a stretch and LaMarr is always a welcome sight onscreen.

John Gertz as Dr. Gustavo Bauer.

On the personal front, wedding planning is set aside to further explore what the relationship between Alexis and Beckett (Stana Katic) is heading toward. When we last saw her, Alexis was exchanging first-world problems with a famous pop-star and came to the revelation that her father probably did know best about the whole Pi situation. The story picks up here with Alexis following through with the breakup, and finding herself caught between a rock a hard place.

So what’s a girl to do – go home and admit Dad was right after all, or suck it up and pay the bills as a form of self-flagellating penance? Enter Beckett, who picks up on Alexis’ quandary and meets up with her surreptitiously to offer her own advice.

Whether or not you think Alexis’ character has overstayed her welcome in the Castle universe, this is still a well-written sub-plot to show Beckett further integrating herself into Castle’s family. Katic offers a vulnerability that doesn’t stray into the saccharine and ultimately brings healing. Though no worries, her tough-as-nails side is back in full force next week when she heads on a dangerous undercover operation in the New York underground.

Castle returns next Monday with “In the Belly of the Beast” @10pm on ABC.