Doug and Judy both go undercover as Doug Fisher and Judy Robinson to watch Johnny Hartman, a talented young pitcher playing for his high school team, the Tigers, with the feds also wanting to be kept up to date on whatever happens. Doug soon establishes himself as a hitter as well as a catcher, while Judy is placed in all the same classes with Johnny, whose home life is anything but ideal as he seems to have a great deal of resentment for his father, and the house is constantly under surveillance.
Johnny and Judy make a connection in class, and he asks her out for that night. After practice, Hennessy, one of the players, is upset that in the last few months Johnny, Doug and another transfer named Jake Whitaker have joined the baseball team and gets physical with Doug. Doug backs off, but Whitaker takes Hennessy down and surprises Doug with his barely leashed brutality. Johnny blows off Whitaker when he suggests getting together that night, and has dinner with Judy. He tells her stories about his childhood and then makes her for a police officer, asking if she's there about his father. Judy doesn't confirm that she's a police officer, but assures him she has no interest in his father. Later, Johnny and Judy head back to his house, where the men who work for his father have detained Whitaker. Whitaker claims to have come by to drop off Johnny's glove, but Johnny is convinced he had put it in his locker (which he had).
Judy reports back to Fuller, who finds it interesting that Johnny is so concerned about his father, and also that Whitaker seems so interested in Johnny. He assigns Hanson and Ioki to look into Jake Whitaker to see what they can find out. Judy and Doug return to their undercover roles for the big game that day. Doug hits all foul balls when he first comes up to bat, and when the teams switch, finds himself in the catcher's position as Johnny pitches. Johnny's first pitch is dead on, but once he spots his father he loses concentration, and his next few pitches go wild. Doug later scores a hit that allows all the basemen to get home, and the Tigers win the game. Meanwhile, Hanson tricks the secretary into taking him to the nurse's office so that Ioki can get a look at Whitaker's records.
At the celebratory party later that night, Johnny speaks briefly with his father, Judy by his side the entire time. Whitaker comes up with his mother, Grace, who seems unpleasantly surprised to see Frank Hartman. Frank excuses himself, and Grace pumps Johnny for information about where he lived prior to this year. Johnny hedges, and finally says that he lived in Connecticut, but that they moved around a lot. Frank is talking to Coach Wilson, and telling the other man that he wants Johnny to play ball in college for at least a couple of years before trying to the big leagues. Frank then elicits a promise from a confused Wilson that the coach will look out for Johnny and his career should anything happen to Frank. At the fed's request, and with a last minute search order, Ioki and Hanson head to Whitaker's home, where Ioki finds a picture of Whitaker's mother, Grace, with an older gentlman. Before there search can go much further, Whitaker confronts them with a double-barrelled shotgun. After firing one shot, Whitaker gets physical with Hanson, and is subdued by Ioki. Ioki tells Whitaker that they're police officers, and he states that he is as well.
Back at the chapel on Jump Street, Fuller and Spencer Phillips, the FBI agent in charge of Hartman's case, question Whitaker. He's a first class detective from New York Midtown on two weeks vacation named Danny Jacobson, Jake, age 25. He reveals that Frank Hartman's real name is Carmine Terranova, and he's a federal witness against a mobster named Nick 'The Iceman' Lucchesi. Fuller's more than a little upset to learn that Phillips has been using his team to watch Terranova's son Chris (Johnny Hartman), but Phillips doesn't want to give them any more information, telling them strictly to keep an eye on Johnny Hartman. He admits to having found Johnny by keeping an eye on the papers. Phillips antagonises Jake until he admits that Lucchesi killed his partner. The meeting ends when Phillips gets a call advising that Lucchesi's boys are in town, and Jake offers to find them. Fuller pairs Jake up with Hanson, and tells Doug and Judy not to take their eyes off Johnny.
Jake shakes down a snitch in a club, leaving Hanson upset at the level of brutality that Jake is willing to use to get what he wants. Jake's methods continue to deteriorate, as he gets the information about the Lucchesi boys' room by dunking the hotel manager in a fish tank until he talks. Hanson gets up in Jake's face while they're searching the room, but Jake is amused rather than offended. On the field, Judy admits to Johnny who she is, and he shares with her his unhappiness at having to constantly change his identity, even though he does it with a smile. Back that the chapel, Jake shares a pizza with Doug and Hanson as Phillips tells Fuller that Frank wants to see his son one more time. While Doug picks up Judy and Johnny from Sharkey's, a local pizza joint, Jake calls someone and tells them where Frank is. The four leave together. Back at Jump Street, Ioki shows Fuller that the woman Jake claims he paid to pretend to be his mother has a connection to Jake's dead partner, Marty Spaulding.
Hanson and Ioki confront the woman, who reveals to them that it was Frank Hartman who killed her husband, not Nick Lucchesi. Hanson and Ioki realise that Jake is there to facilitate Frank's murder rather than protect him, and after Mrs. Spaulding rips the phone cord out of the wall, Hanson and Ioki head out with the intent of saving Hartman's life. Johnny is meeting with his father at the hotel, and while Frank tries to reach out to his son, Johnny still wants no part of Frank. Frank finally backs off and apologises for ruining Johnny's night, but despite his harsh words, when Johnny turns back to the window there are tears in his eyes. Phillips and Fuller arrive at the hotel in time to arrest two of Lucchesi's thugs, while Jake watches, crouched behind a police car, which he then enters in order to take out a police rifle -- determined to take Frank Hartman out himself.
Hanson and Ioki show up shortly before Frank Hartman is walked out of the hotel. From his vantage point next to the car, Jake shoots at Hartman. He misses, and the agents with him rush him back into the hotel. Jake jumps in the car and begins driving down the street, heading straight for Hanson. Hanson fires at the car, which goes up over another car, flips over, and then lands on the roof. While the police arrest Jake, Hanson cocks the rifle that he used and tells Hartman that's how Jake would have done it. At the game, Johnny tells Judy that he'll be moving again with a new identity, and they both agree that they'll always remember his time as Johnny Hartman. Coach Wilson brings a scout over to meet Doug, who tells him that he's really a police officer. The scout is still interested.