The murder of a venture capitalist by an exotic supercharged poison gets Beckett (Stana Katic) assigned to protect the real target, charming billionaire inventor Eric Vaughn (Ioan Gruffudd) whose mutual attraction to Beckett doesn’t go unnoticed by a jealous Castle (Nathan Fillion).Incentivized to solve the case as soon as possible, the mystery writer jumps headfirst into the investigation with Ryan (Seamus Dever) and Esposito (Jon Huertas), but they hit a snag when the busboy who poured the poison on the entree turns up murdered as well.
Beckett discovers the poison likely came from an university lab hired by the billionaire to find an antidote to an entire class of neurotoxins and run by a lead researcher (Erin Cardillo) still angry of her spurned romantic advance and with easy access to both the poison and the restaurant. Esposito calls in NYPD tech Tory Ellis (Maya Stojan) to help identify the gun for hire (Russ Bain) who is caught from the back on security camera handing the bottle of poison to the busboy the night of the murder.
Seeking shelter and condolence from his loved ones, Castle returns home to the comforting shoulder of Alexis (Molly C. Quinn) and the not so reassuring words of wisdom from Martha (Susan Sullivan). A second attempt of Vaughn’s life leads to a series of puzzling connections between Vaughn, his murdered business associate, and a fake Mexican energy company owned by the billionaire which authorized the cash payments for both the poison and the hitman with the approval of its boss, Eric Vaughn. Or to be more exact – his right-hand man (Scott Rinker).
Castle’s jealousy is fun to watch, particularly because its deserved as Beckett allows Vaughn to kiss her before pushing the charming millionaire away. It’s also interesting to note that for the second time this season an episode foreshadows possible problems in Castle and Beckett’s future, both times around the idea of Castle’s failure to commit (which is odd because their entire relationship has been about Kate’s reluctance to admit and act on her feelings for the mystery writer).