While Homer is watching another episode of I Can't Believe They Invented It!, Bart takes a moment to ask him for permission to use the power drill. He gets sent to the basement. Homer continues watching and Bart can't find safety goggles for the power saw. Homer advises to just turn his head if stuff starts flying. Homer hears of a terrific sounding deal and tries to dial, but must answer the door for Patty and Selma. They are taking Marge out to have their hair done. Marge advises Homer to do something with the kids while they are gone. When Homer asks Lisa for the quickest, easiest, cheapest way to entertain her, she suggests going to the video rental store. On the way out, Homer notices Bart is wielding with acetylene torch, not bothering to ask about anything.
At the beauty salon, Patty gives Marge a magazine questionnaire to test Homer's Father I.Q. Upon returning home, Marge finds Homer watching a tape called Football's Greatest Injuries. She asks him to take the quiz, but Homer manages to get every question wrong. He denies Bart has any hobbies, but Marge tells him to check the garage. Seeing Bart in the middle of building a soap box derby racer, Homer feels he knows nothing about his son and that he is a bad father.
Concerned about his failure, Homer calls the National Fatherhood Institute and tells them he scored a zero. They send him a station wagon to transport him over there immediately while Bart preaches about building practices of three-time soap box derby champion Ronnie Beck. Martin takes this moment to announce that he is entering the race as well.
At the institute, Homer is given a complimentary copy of 'Fatherhood' by Bill Cosby. He is advised to spend time with his son in order to get to know him better. Back at home, Homer tries to offer his assistance to Bart, but Bart claims he is nearly finished. After he tries reading a part of the book, Homer tries reverse psychology and gets to aid his son. Very soon, Bart and Homer are wearing a pair of "Team Simpson" shirts while they build Bart's soap box racer.
On the day of the big race, among other racers, Bart has a wooden racer called "Li'l Lightnin'" ready for the big race. Martin unveils his racer, a space shuttle-shaped racer called the "Honor Roller". Nelson is racing too, in a orange shark-like racer called the "Roadkill 2000". Bart and Martin agree in the idea that they don't care who wins, as long as Nelson doesn't. Once the race begins, Nelson starts trying to whip Bart into losing, which leaves Martin to zoom past the finish line first. Nelson finishes second, and Bart fails to cross the finish line. Martin's Honor Roller continues at a breakneck speed, all the while he tries desperately to deploy his parachute which fails. He crashes into a wall, and the racer bursts into flames.
Bart goes to see Martin in the hospital. His crash ended with his arm in a cast. Martin claims his racer turned him into a wreck; he finished first, but vows not to race again. Since he is in no condition to race, and under the threat of Nelson winning if he stands unopposed, Martin asks Bart to drive his car. Faced with a dilemma, Bart agrees to drive it.
At home, Homer informs Bart that in order to win the next race, they will need to do a lot of work on their racer. On the other hand, Bart has other plans. He decided not to race in the 'slow, ugly shopping cart' in favor of Martin's racer to claim victory. He wants to do so in order to win. Bart tries to apologize, but this news only upsets Homer. Homer tells Bart to go on and win without his dad, and see if he cares. Bart leaves Homer to sit in the racer they built, which soon crumbles under Homer's weight.
When Bart is ready to go off to the race, nothing is about to get Homer to budge from the couch. Marge takes this moment to express that she has always defended him when he is insulted. Disappointedly, Marge relents, saying maybe he is a bad father after all. When Homer goes to the refrigerator, he takes another look at the fatherhood quiz. This time, he starts to take the quiz again and answers every question correctly. With renewed confidence in his status as a perfect father, Homer is on his way to the derby.
At the soap box derby finals, Bart half-heartedly listens to Martin's coaching. However, upon seeing Homer in the bleachers, Bart's doubts at home disappear and eagerly accepts Nelson's taunt. The race goes on, and no matter what Nelson does in attempts to cheat, Bart is able to win.
Bart is awarded a racing trophy from his hero Ronnie Beck. Nelson offers to congratulate Bart, but Bart sees this as an opportunity to taunt Nelson for losing. Marge tries to make him stop due the idea of a 'bad winner', but Bart's moment of victory has him continue with Homer at his side. The National Fatherhood Institute, witnessing the event, cheers seeing Bart and Homer functioning together in harmony.