Two officers enter a museum basement and find a security guard, who tells them that he's an ex-cop - and they're not police. One draws a gun. The guard shoots them both. One of the fake cops is killed, while the other is wounded.
When curator Sydney Carlton warns Ria that this shooting better not have anything to do with the employees she vetted, Cal warns him not to blame her to try to save himself. Then Cal goes to the hospital and asks the wounded man what he was trying to steal and for whom. The man says that the item was pre-sold, then he slips into unconsciousness.
In the waiting room, Cal notices a man eying an agitated woman. Cal sits beside her - preventing the man from doing so - and asks why she's there. Concern for a co-worker, says the woman, whose name is Naomi Russell. When a nurse tells Cal that the wounded man died, the man watching Naomi leaves.
Carlton tells Gillian that he thinks the attempted robbery was an inside job. Gillian replies that Ria vetted everyone except him - and Cal says to expect a second try.
When Naomi asks Cal to join her for coffee, he asks why she's so afraid of the man who was watching her. Jack is an ex-boyfriend, she explains. Cal says to call him if Jack shows up again.
Back at the office, Gillian mentions that one hospital janitor wasn't wearing an I.D., while Eli says that the museum uses the same people to repaint the walls for each new exhibit - and they weren't vetted. Ria explains that Carlton never asked for that.
Then Naomi texts Cal, saying that Jack is harassing her in her parking garage. Jack hurries away - in a car with government plates. He's with Immigration & Customs Enforcement, explains Naomi, who wants go somewhere else. Cal takes her to his house, where she flirts outrageously.
Meanwhile, Gillian and Eli watch Ria question the painters. One is an illegal immigrant, who knows nothing about the attempted robbery. The second is an aspiring artist named Al Larson, who says that Carlton orders town cars, pays cash, and never gets in them. (Drug deal alert!) Eli then shows Ria hidden camera footage of Larson thumbing though the new exhibit's catalog in the lobby pre-interrogation, noting his false disinterest in an Egyptian statue and an Indian emerald.
Ria and Gillian confront Carlton about Larson's town car revelations. Carlton admits to buying drugs, but he denies involvement in the robbery.
Cal and Naomi's first kiss is interrupted by Jack breaking into Cal's house. But Cal grabs a gun, gets the drop on Jack, and orders him out. As he leaves, Jack asks Cal why the world's greatest deception expert can't see the world's biggest liar. When Cal asks Naomi if she has anything to add, she replies that Cal's crazy for her. Cal spits back her previous line about always jumping into things too quickly.
Back at the office, Cal orders Ria to take a look at Naomi - who's just ducked into the ladies' room - and tells Gillian that Naomi is trying to play him. Meanwhile, Eli introduces Larson to Cal, who claims to be interested in buying his art, then accuses him of being part of the attempted heist. Larson admits that he'd met Naomi and the two now-dead men, but Naomi is not into guns and her ex-lover Jack's having a hard time letting go. Cal orders Larson to meet with Jack - or face charges.
Cal and Ria watch this meeting, and Ria is amused that Naomi used Jack to play Cal. But Cal says that he's not finished with Naomi and meets her at his home. Cal tells her he knows that Jack's customs job enabled him to move stolen art, as Naomi fakes surprise. Then Cal asks her to accompany him to the opening of the exhibit. Naomi is thrilled.
As Cal and Naomi stroll through the reception, she dismisses the emerald as "just a rock" and heads for the bar, where she hands a man a drink. Meanwhile, Cal tells Ria that Naomi purposely avoided contact with a janitor at the hospital and to look for a white-haired man in his sixties. (Eli and Gillian are also watching the crowd.)
Naomi brings Cal a drink and makes a quick trip to the ladies' room. She returns and gives Cal a kiss that's interrupted by the man to whom she gave that drink collapsing to the floor - and the sound of an alarm. Cal says don't worry, the man's just been drugged. But the emerald is missing! Cal runs outside and watches a white-haired man smile from the back of a cab that's driving away.
Cal confronts Naomi, who admits that the emerald is heading back to the temple from which it was stolen in 1908 and that she was partnered with Jack, who got tired of her Robin Hood act, so she dumped him - but he wouldn't take no for an answer. She also blames Jack for getting her friends killed and says that she enjoyed toying with "the great deception expert."
Cal realizes that she was just a decoy who needed to attend the reception so the heist could take place. Naomi asks Cal if he wants to get dinner. He walks away.
Back at the office, Gillian's angry because Cal let Naomi escape. Cal explains that he had Carlton replace the emerald with a fake, so Naomi got nothing. When Gillian asks why he didn't tell her, Cal replies, "It's cat-and-mouse, not cats-and mouse" and walks away.