10/14/2014 03:29 pm ET Updated Dec 06, 2017

Castle Recap: Caskett Battles An Invisible Murderer In 'Clear And Present Danger'

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“Clear And Present Danger,” the third episode of the seventh season of “Castle,” was all about things we couldn't see, from invisible men to missing plot lines about Castle's disappearance. But even though this episode didn't touch on the subject that's been the major plot point of this season, it was a well deserved and very funny break.

The episode begins with Castle and Beckett lounging in the author's living room trying to figure out plans for the evening. When it becomes obvious that they'd like to stay in for the night, Beckett's phone rings. For once we wish she’d ignore it, but she wouldn’t be Beckett if she did. It turns out the death of an anarchist foils their night in and the case of the invisible man begins.

That’s right, this case is all about an invisible murderer, making it pure Castle nerdiness perfection.

Will Fairwick, an insurance claims adjuster turned pool-hustler extraordinaire by night, has been found dead in his apartment with a pool cue sticking out of his chest. As the team starts the investigation, every clue points to some invisible force having killed Fairwick: from a security video of the hallway showing his door apparently opening by itself to items magically disappearing from the evidence room even though the officer swears Beckett is the only one who entered.

Castle is sure it must be the work of the Devil himself, since before he died Fairwick insisted his magnificent pool abilities were due to a deal he made with the lord of darkness and that now “his time was up and that he was about to lose his soul.”

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After interviewing an angry felon who’d been hustled by Fairwick, Castle and Beckett learn that there was another apparent victim of this invisible force. Tom Talmadge, creator of an app called Hytch (think Uber or lyft), has been attacked in his brownstone but is unable to describe who did it.

Phone records then lead the team to Fairwick’s girlfriend, Donna Brooks. The biologist used to date the victim when they studied at MIT together, before he suddenly dropped out. Recently though, they had reconnected and the flame was rekindled.

Frustrated and out of leads, Beckett and Castle head to the victim’s apartment to find his keycard and are suddenly attacked by the invisible man! Or force, or the devil -- but the point is that it's invisible. Thanks to some quick thinking by Castle they are able to hold on to the keycard, while the invisible thing gets away with Castle’s credit card.

The keycard leads them to a top-secret government facility where Fairwick worked. His current project was, of course, an invisibility suit (think Harry Potter's invisibility cloak but made with top-secret government money.) Being an anarchist at heart, Fairwick usually joked he’d sold his soul to the devil when he took the job.

The duo discovers that the lab had been cyber-attacked before they’d been able to actually complete the suit. A symbol in the line of code leads them to the victim’s neighbor, Henry, a super-hacker and online gaming god who was friends with Fairwick.

It turns out the two geniuses had been able to complete the suit themselves. They’d used it to break into Talmadge’s brownstone to try to find evidence he’d stolen the code for his app from Henry. But when Talmadge unexpectedly arrives, Henry attacked him while wearing the suit. They realized, then, that the suit “had turned Henry into Frodo” and that it was too much power for anyone to have, so they decided to not give it to the government.

Henry then unveils a key piece of evidence, Fairwick’s inspiration for the suit’s technology had come from the cuttlefish, a master of camouflage, and also one of Donna’s pets. Donna confesses that she realized Fairwick was only using her for her research and then used his suit to kill him. So it turns out the girlfriend did it.

After closing the case, Castle and Beckett finally get the alone time they’ve been denied throughout the episode, first due to possible invisible men in the room and then to Martha walking into their zombie-inspired trap.

Worth Noting:

-Everything Ryan and Espo in this episode was fantastic, from Ryan’s job as security at a male-stripper club and telling Espo that “ladies be crazy” to Espo’s reaction when he thought Ryan might be cheating on Jenny. He’s not, of course.

-We are no closer to knowing what happened during the time Castle disappeared but it doesn’t matter because this episode was pure Castle charm perfection.

-Kate’s face telling Castle that he “just kind of makes nerdy sexy” while he’s setting up a trap in his room with pots and pans is adorable, and we agree with her.

-Castle’s enthusiasm at finding an underground gaming den and then taking down Henry with the Falchion sword, we insist, so much Castle nerdy charm in this episode!

Quote of the week:

Castle to Beckett after setting up the trap: “And you thought zombie apocalypse survival camp was a waste of time.”

"Castle" airs on Mondays at 10:00 p.m. EDT on ABC.