Jake is sparring with a dummy and manages to demolish it. Kyle arrives to tell him "it's time" and they're off to… sexual harassment class. Jake uses his enhanced hearing and overhears a report from the control room, a scrambled com from Vienna. In Vienna, the man on the phone makes a deal, says he'll be in Washington on Monday, then kills the man in the office.
After the weekend, Jake finds out that Diane went out on a date with a cryptologist, Steve Clemens, and Jake is mildly jealous. He gets a call from Sarah and they set up a date. Beckett then has Jake tap into a phone call and they determine the speaker is a Polish mercenary, Vasily Koronkiewicz. They're not sure what he's after and Kyle figures they should talk to Seymour LaFortunata, a researcher in the basement. They show him Vasily and he goes to work, then get a hit from a facial recognition scan leading them to a bank. The bank manager wants a subpoena and Kyle distracts the man while Jake taps into the computer and gets the routing number of Vasily's employer.
After a long night Jake goes to see Diane, who suggest he go to a movie and rushes off to her date with Clemens. He invites Jake along but he declines and goes back to work. The next morning Jake gets a match and he and Kyle head off to where Vasily was spotted. They go there and spot him, giving pursuit into an alleyway. They get separated and Vasily attacks Jake, stabbing him in the stomach before running.
They get Jake to the lab where his nanites heal him. Jake is more concerned about how Diane spent the night with Steve and brings up his files. The team try to track down Vasily without much luck but Jake comes up with a name and talks to LaFortunata, who runs down the lead. That night Jake meets with Sarah, and they run into Diane and Steve. Sarah asks Diane a few pointed questions about their job while Steve and Jake compete (Steve wins twice), and discuss Diane's feelings for Steve. Jake eventually competes at the bell ring hammer… unaware that Vasily is watching him until a minute or so later. He bows out on Sarah and goes after the mercenary, telling Clemens to call it in. Jake goes after him in the parking lot and tries to sneak up, but Vasily knocks him down and comes at him with a knife. Fortunately, Clemens arrives and takes him out, although he's on the edge of shooting Vasily.
Kyle confronts Vasily in his cell but the man is unimpressed. Diane is checking out Jake's wounds and a jealous Jake mentions that he's divorced. Diane isn't thrilled but Jake wonders why Clemens had a gun with him. Jake finally admits that nobody can know the real him, including Sarah. Diane assures him she'll be there for her and he can't cut himself off from everyone else. That night Jake meets with Sarah and comes clean with her. Meanwhile LaFortunata contacts Kyle and Beckett with news: Vasily is working for a Mafia syndicate to acquire a living subject with advanced bio-technology, and they figure out he's after Jake.
Sarah is skeptical of Jake's claim and slaps him, believing he's lying to her. After she goes off, Kyle arrives to pick him up and they go to ask Vasily why he didn't capture Jake the first two times. They find Vasily dead, his throat killed, and Jake suspects Clemens. A security check reveals Clemens was there, and they figure he's going after Diane. Clemens is taking Diane by car for a "surprise."
The team runs a check through security cameras and pick up Clemens' license plate and location. He's taken Diane to a dock for a "pleasure cruise." NSA agents head for the dock as Clemens takes his boat out. Jake manages to super-leap on-board and Clemens draws a gun on him. Clemens boasts of his scheme and Jake takes control of the computerized navigation, distracting him long enough for Jake to go for the gun.
Later at Jake's apartment, he and Diane play Bobble and commiserate over their messed-up love lives. Diane flirts briefly with him but they end up playing Boggle.