Castle (Nathan Fillion) must have been a good boy this season, because the penultimate episode plays right up his conspiracy theorist's alley. He also gets to play with a toy tank, and after he navigates it through a pretend minefield, he discovers that the tank's camera can bit used for a bit of naughty, bedroom spy work.

Yes, 'The Human Factor' is very kind to our titular character indeed.That's a good thing, because with the groundwork laid for this episode and the trailer aired for the finale, the landscape of Castle could be changing. How drastic the change will be is still up for debate, but that's getting a bit ahead of things for now. Because for now, the only issue Castle and Beckett (Stana Katic) have to work through is how to investigate a murder with no crime scene, no body, and no solid evidence to go on.

It's a nice twist from your typical case: the dynamic duo gets a call to a crime scene, but by the time they get there, the feds have swooped in and are effectively keeping the local detectives in the dark.

Fortunately, Kate Beckett is like a dog with a bone when it comes to tracking down bad guys, and nothing the higher-ups throw at her can deter her progress. Inch by inch, she, Castle, Ryan (Seamus Dever) and Esposito (Jon Huertas) track down the clues that will lead them to whistleblower Dale Tanner's killer.

Most of the heavy-lifting in this episode is done by Kate - with some late night assistance from Ryan - while Esposito lurks in the background providing support and Castle entertains one wild theory after another. He muses aloud about drone armies and fixates especially on the "rise of the machines," only to be disappointed that it is, as always, the work of mere mortals. Calling the federal agents at the scene "Agent J" and "Agent K" and referring to the drone cornfield attack as being just like "North by Northwest" only adds to the fun. Bonus points if you caught the Star Wars reference.

In the end, however, this episode belongs to Kate. Stana Katic owns the role of the strong, sharp female detective like never before. She's the one who smells a rat from the beginning. She pushes and pushes despite all the odds stacked against her, and for her trouble, she manages to get the drop on one of the Attorney General's special investigators, Jared Stack (Carlos Bernard).

At first, Stack is more interested in using Beckett for his own agenda, but as the episode unfolds, so does a grudging respect for her abilities.

As she weeds out one red herring after another, Stack's attention becomes more evident, but where Erik Vaughn (Ioan Gruffudd) vied for her romantic attention a couple of episodes ago, Stack is more interested in her on a professional level. When all is said and done and the victim's angry son is dragged away, Stack pulls Beckett to the side and makes his pitch.

He asks about her future and compliments her skills and her sharp mind, then offers her a job working with him for the Attorney General. She's one of the elite and he knows it, and when she falters, he points out that he started out in homicide, too. You can almost see her weigh the pros and cons in her own mind as her career flashes before her eyes.

And with that, the foundation is laid for a potentially explosive season finale. Clearly, the premise of the show isn't going to be altered, but what do you think would be the perfect cliffhanger ending to leave fans begging for more come fall? What choice should Kate make?

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The season finale of Castle airs May 13th, 2013 @10pm on ABC.