Things are a little awkward between Castle and Beckett. They’ve been watching a lot of movies lately, but haven’t been doing much else recreationally. That includes certain activities in the bedroom. Neither felt the other was quite ready. However, both parties are more than ready. Too bad there’s been another pesky murder.
Will Fairwick was impaled with a pool cue in his apartment. He bled out in minutes. The victim had $20,000 in cash in his sock drawer. His video game-loving neighbor, Henry Wright, says Will was a pool hustler. Fats Shepherd, the owner of a high-end billiards parlor, says the victim once claimed he made a deal with the devil. Will believed his time was up. He was going to lose his soul. Video footage shows what Castle believes to be the killer exiting the victim’s apartment. No one else can see him though. That’s because the killer is invisible.
Ryan learns that Will hustled an ex-con named Jiggy Michaels out of $20,000. That’s the amount found in the sock drawer. Jiggy claims Will was interested into breaking into a brownstone. There was an intrusion at the place earlier in the week. Tom Talmadge, the founder of a lucrative rideshare app, was assaulted during the break in. The guy claims some force threw him to the ground. Talmadge blacked out for a bit. When he came to, he saw Will Fairwick standing above him. Talmadge believes this stranger saved his life.
When the video footage from before goes missing, Castle surmises the killer is an invisible man. Will had a relationship with Donna, a biology professor. They first met at M.I.T. Will had a breakdown during his freshman year. His present day job at an insurance company was a front. He had a well-used keycard for an office he never visited. When Beckett tries to grab the keycard from the victim’s apartment, she’s choked by an unseen force. Castle is thrashed, too. He manages to hang on to the keycard as the invisible assailant flees.
Castle and Beckett take a break from the case to get back to business in the bedroom. Too bad they both have the feeling they are being watched. Castle sets up a booby trap to catch any invisible intruders. It also works the visible, as Martha is conspicuously caught in Castle’s concoction of clanging cookware. In other news, Ryan knows that college for his newborn baby girl is going to cost a cool quarter of a million dollars. So he picked up a second job as a bouncer at a strip club—a male strip club.
Castle and Beckett follow a lead that brings them to a secret government facility where Dr. Elena Sarkov explains the Will worked for her as a quantum engineer. His M.I.T. flame out was a ruse. They were working on cloaking technology at the lab, but haven’t been able to get it to work. Elena suggests that the Chinese may have been able to do so in the wake of a recent cyber-attack. The deal Will made with the devil was with the government. His death sets the research team back years.
A symbol that is in the virus from the cyber-attack matches the one seen on the t-shirt that was worn by Will’s neighbor, Henry Wright, who is the hacker. The guy attended Cal Tech with Tom Talmadge. Henry claims his old college chum stole the code that was used to build the rideshare app, thereby costing him billions. Castle uses his video game knowledge to help track down the suspect. Henry claims he didn’t murder Will. He’s afraid that the same people who killed his friend may come after him next.
Castle and Beckett realize that the reason the victim got back in touch with Donna was so he could access her research. Will wanted to destroy the cloaking suit technology so it wouldn’t fall into the wrong hands. Those hands ended up belonging to Donna, who was angry at how Will used her. He never saw this scorned woman coming. Now Castle and Beckett can’t see her going, as Donna slips on the cloaking suit. They manage to hone in on her through some nifty fire extinguisher shooting. The invisible woman is captured.
With the case is closed, Castle uses his night vision goggles to make sure that the coast is clear in the loft. He and Beckett can pick up where they left off. All she needs to do now is slip into something special. However, it’s not the sexy outfit Castle got her for Valentine’s Day. No, what she’s wearing is even better than that. In fact, it’s invisible.