Weird Ernie calls Sam in from the barbecue to have him take a questionnaire to confirm Bird Dog's (joke) theory of memory loss at high Mach speed. As Sam leaves, they wonder if they're going to make a major discovery, or are the target of a practical joke.
Sam looks at the X-2 in the hangar and Al appears. He confirms that Sam still has memory loss, and explains that the project was intended to let someone travel within their own lifetime. Sam remembers bits and pieces of it, but can't remember the year and Al won't tell him. He explains that Ziggy thinks that something was waiting for Sam to travel in time so it could use him to fix something in Tom Stratton's life. They figure once Sam saves Tom, who was killed trying to break Mach 3 in the X-2, they can bring him back to the present. Sam insists there must be another way. The next most likely scenario requires Sam to be ground zero at an atomic detonation, and only has a 52 percent chance of success. The odds get worse after that. Al suggests he just wait and do nothing, Tom will live in the future, and Sam will eventually "arrive" in his own time. Sam warns he can't go on pretending he's Tom, but Al points out that Peggy and Mikey would have lost Tom anyway. Sam worries that he can't fly, but Al says that he can be his copilot. He was an ex-astronaut and says the test flight is easy. However, Sam can't land the X-2 even with his help, so they realize he'll have to eject and let the X-2 crash.
That night, Sam considers calling Indiana again to reach his family. Peggy comes out and figures he's worried about breaking the record the next day. She assures him that he can do it, but asks him to promise without telling him what. Once Sam does, she says she'll tell him tomorrow night what he promised.
The next day, the X-2 is attached to the bomber. Sam hands in the questionnaire and Dr. Berger looks at in amusement.
The pilot's wives are at home and listen as the planes take off. Outside, Mikey watches his father fly off into the sky.
On the ground Berger shows Weird Ernie Sam's questionnaire. Since Sam couldn't remember anything about Tom's life, he filled in the questions with his own life. They have no idea what most if it means. They figure he's playing some elaborate practical joke as a hoax.
As Sam prepares to leave in the X-2, LaMotta tells him that right before he got the fire warning light, he smelled coffee brewing. Sam enters the X-2 and wonders where Al is. He has no choice but to get in and the technicians seal him in tight. The bomber levels off and LaMotta drops the X-2. Al appears in the cockpit with Sam and walks him through the procedure. The X-2 takes off and Al has Sam match his hand movements.
Al explains he was running late due to a play-off game and an after-game date with a hot woman. The X-2 passes Mach 1 and then Mach 2. They hit 70,000 at Mach 2.4 and level off. Al then tells Sam to punch the third rocket and the skin temperature rises as they accelerate to Mach 3. Sam hears the same bubbling noise and the fire warning light goes off. Sam realizes that LaMotta heard a percolating noise, he didn't smell it. Al realizes that the fuel is boiling because of the heat. Sam shuts down the rockets and the X-2 plummets toward the ground. It explodes… and Sam parachutes to safety. As the emergency squads arrive, Sam realizes that he hasn't returned to his own time.
As they head back, Al appears to Sam and admits that their theory about putting things right doesn't appear to be right. He suspects that Sam might leap back at any time, and heads back for the woman he ended up in bed with after the game.
Sam arrives at the hospital and greets Mikey. Berger tells him that Peggy went into premature labor when she heard the crash. Sam reassures Mikey and goes to see Peggy. She says she's proud of him and then starts feeling labor pains. Sam directs her through basic Lamaze procedure, relieving her pain, and then says he learned it in premed.
Berger calls him outside to meet with Dr. Blaustein, who warns that the baby is nine weeks premature and they can't transfer Peggy to the neonatal ward in L.A. They recommend having her deliver there and flying her to L.A. The baby won't survive, but at least Peggy will have a chance. Drawing on his medical knowledge, Sam suggests that they stop the contractions by using a beta sympathomimetic. Blaustein has no idea what he's talking about and Sam realizes it won't be invented until the late 1970s. Berger snaps at him but Sam insists his answers were true. He realizes that a 5% solution of alcohol intravenously administered will stop Peggy's labor. Sam explains what will happen and Berger realizes that he knows what he's talking about.
Peggy is soon extremely drunk… and the contractions have stopped. Blaustein wonders how Sam came up with an answer, but Berger says it's better not to ask. Sam kisses Peggy, who says that she loves him. She passes out and Sam kisses her on the forehead. He goes to the window and sees Bird Dog talking to Mikey. Sam calls down and lets Mikey know that his mother is okay. Mikey tosses a ball up into the air…
… and Sam finds himself in the body of a baseball player, just catching a ball. The inning ends with the out and a fan in the stands calls him Fox and tells him to come on in.
The announcer informs everyone that it's the bottom of the ninth and Sam's minor league team, the Waco Bombers, are down by five. If they don't win, they'll be in the cellar for the third year in a row. Sam enters the dugout where the team's mascot barks at him. The coach tells him to do something about the dog, which is Fox's. Sam tries to settle it down without success. Suddenly it backs down as Al arrives and calms it down. Meanwhile, the Bombers get onto second. Sam calls Al off in private and wonders how he got there so fast. Al explains that it's been a week since Sam "quantum leaped" and he's been bouncing around ever since. Al explains he's in the body of Tim Fox, a 32-year-old third baseman. Sam checks the mirror and discovers he has a new face again. Al explains that in a few minutes, Fox will fly out, the Bombers end up in the cellar again, and Fox opens a franchise and marries and has two kids. Sam points out that Ziggy was wrong about what Sam needed to do to leave Tom Stratton, and Al explains that Tom returned to his own body, Peggy and the baby survived, and they named their daughter Samantha.
Al wants to see the game but Sam wants to know what he has to put right this time. Ziggy isn't saying: the computer doesn't want to explain in case it's wrong again. When Sam wonders who created Ziggy, Al admits that Sam did, and that Quantum Leap is his project. When Sam notes that he can't remember anything, Al finally breaks down and tells him that his last name is Beckett.
The Bombers score a home run and are one run behind. Inside, Sam calls John Beckett in Elk Ridge, Indiana. A man picks up and Sam recognizes the voice and calls him Dad. He explains that their fathers are brothers. Sam's "father" John moved to Australia. He tells his father that his name is Sam and John admits he has a son named Sam as well. Sam talks about how he won't be able to get home for Thanksgiving and see his father, and says that he doesn't want to disappoint his father. He hopes his father knows how he feels about him, and John assures him that a father would know if a son loved him that much. John invites Sam to join him in Elk Ridge, for Thanksgiving or any other time. Sam says goodbye and whispers "I love you, Dad." After John hangs up, he goes out to the barn to help his son Sam, and tells him that his brother's son may visit them some day.
Sam says "thank you" to whatever force allowed him to speak with his father, and realizes he can make the world a better place. He runs out to the field and thanks Al for giving him his last name. Sam thinks that he's there to win and starts to go out. The coach says that it's his last year and he doesn't want to end it in the cellar. Sam takes the field and gets two strikes. The pitcher throws the third ball… and Sam misses. However, the catcher drops the ball and Sam runs for first. The first baseman misses the catch, gets the ball, and throws to third, but the third baseman misses as well. Sam runs for home and slides in, safe.
As Sam's teammates surround him, he disappears in a flash of blue light… and finds himself standing at the front of a classroom.