At Western Tech, the students announce the final round of the annual Fizziks Follies. The four finalists are: Hillary Chapman, Geoffrey Kramer, David Ryman, son of the campus professor, and finally Aaron Turner. MacGyver arrives on a visit to his old alma mater and to help judge the barricade contest. David greets him and MacGyver congratulates him as a finalist. David is clearly eager to win. MacGyver goes into the physics hall to meet with Professor Ryman, and stops to admire the photos of previous barricade winners, including himself. Professor Ryman is pleased to see him but is disappointed that he went in other directions. Professor Ryman is more interested in David’s grades then how he’s doing.
As they head to Ryman’s class, David talks to his girlfriend Janet, who notes that he’s been obsessing about the barricade contest. Professor Ryman comes in and introduces MacGyver as a class observer and a referee in the contest. He has the students present their experiments in low-temperature super-conductors. He praises Geoffrey while MacGyver notices that David has a leak in his plumbing. David uses a spectrometer to pinpoint the leak and Professor Ryman tells David to improvise. He notes that MacGyver could do it and then takes a piece of gum from a student and uses it to fix the leak. Professor Ryman is clearly disgusted with his son’s lack of intelligence, while Geoffrey smirks. MacGyver consoles David, who says it’s not a problem. MacGyver then talks to Professor Ryman privately and says he was too rough on David, humiliating him. Professor Ryman insists on not showing any favoritism toward his son.
After class, David complains to Janet and insists that his father will notice him once he wins the barricade contest. He then offers to show Janet his top-secret barricade and takes her to his dorm room. They go in, unaware that Geoffrey has observed them. He goes into his room across the hall and uses a parabolic microphone to listen in. David explains his barricade: a garage door opener mechanism that barricades the door. His secret is a miniature model of the room, including the barricade which closes and opens. The peephole has a periscope which leads to the model. When the miniature barricade is closed, the real barricade is open and vice versa. When someone uses a scanner to open the barricade, they’re actually closing the barricade. Janet is impressed and Geoffrey is satisfied that he has the solution. However, Janet notices that David has a stash of speed to stay awake. He says he’ll stop using them once the contest is over, and shoves her away when she tries to take them. She runs away and David lets her go.
The next day, MacGyver starts the contest: the last person with a barricade standing is the winner. David apologizes to Janet but his father calls him away to the contest. Janet tells David to go win and she’ll talk to him later. MacGyver approaches her and she explains that David has been working on the barricade for months to show his father he’s worthy, but Professor Ryman has no idea what he’s doing to David. She blurts out that David is taking drugs. MacGyver wants to talk to David but Janet asks him to wait until after the contest and they’ll both talk to him. MacGyver reluctantly agrees.
First, Geoffrey tries to get through Aaron’s door. The barricade has 12 dead-bolt locks that lock and unlock in various combination. David is assigned to work on Hillary’s door. The key is a scale with two glasses, one of wine and one of water. David has to tilt one or the other to trip the electrical circuit. David explains his barricade to Hillary, and Geoffrey shows his barricade is a time lock. As they begin, MacGyver tries to talk to Professor Ryman about David and the pressure he’s under but Professor Ryman ignores him.
Hillary finds the right frequency for the garage door opener, while David gets a loudspeaker and oscillator for Hillary’s door. Geoffrey uses filings to magnetize each lock on Aaron’s door to determine if it’s open or closed. Professor Ryman congratulates him and then observes David. David generates a high-pitched sound wave and shatters one of the glasses, tipping the balance, completing the connection, and opening the barricade. Geoffrey gets his door open a few seconds late.
David goes to get a frequency converter and boosts the electrical frequency of the time lock. Geoffrey, already knowing the solution to David’s barricade, simply holds out until the last minute and then “finds” the solution just before David completes his solution. Janet tries to console David, who tells her that his father is right and he is a loser. As Geoffrey and the others leave for the celebratory party, MacGyver looks into David’s room and sees how the barricade works, and realizes that Geoffrey never looked into the room after opening the door.
At the party, David is gone. MacGyver approaches Professor Ryman and tries to explain that David is suffering from burnout and taking drugs. Professor Ryman refuses to believe any of it and MacGyver approaches Geoffrey. He asks Geoffrey how he figured out the barricade and the student is unable to provide an explanation for how he figured it out. Geoffrey explains about the periscope but MacGyver points out he never looked into the room after solving the barricade. Everyone realizes Geoffrey cheated and David should have won. Geoffrey storms off and Professor Ryman goes to find David.
MacGyver and Professor Ryman go to the physics building, where David is drinking heavily in a laboratory and taking speed. Professor Ryman boasts that David couldn’t be taking drugs if he won the contest. Janet reveals David has called her and said he’s barricaded himself in the physics lab. Professor Ryman tries to explain he won but David says that he built the ultimate barricade: he’s wired the building and built a bomb. MacGyver tries to get through to him without success, and Professor Ryman doesn’t have any luck. MacGyver goes over to the lab and Professor Ryman insists on going with him. Janet blames him for putting pressure on his son, and tries to talk to David while the men head over to the lab.
MacGyver and Professor Ryman arrive at the lab and the professor explains there’s plutonium stored above the physics lab. They get to the door only to discover that David has set up a motion sensor and an electrical arc to shock anyone coming in. David hangs up on Janet and Professor Ryman tries to keep him occupied while MacGyver tries to find a solution. David talks about the swim meet his father never showed up for and the Christmas presents he forgot. He tests his father on his birthday, and Professor Ryman doesn’t have a clue. Professor Ryman tries to explain about the plutonium but David doesn’t believe him. David collapses from the drugs and alcohol and MacGyver returns with a mix of acetic acid and ammonia. It forms a smoke screen and they get past the motion sensor.
Inside the lab, they discover the bomb and realize it only has a few minutes remaining. MacGyver tells Janet to warn the campus police but there’s not time for anyone else to get there. Professor Ryman tells MacGyver to get David out, but MacGyver says they’ll both have to work together. The bomb has a collapsing circuit with a mercury switch trigger. The mercury is in a glass dish: it if touches any of the contacts on the dish, the bomb goes off, and the timer tilts the dish in four and a half minutes. They start to open the case but realize the screws are also wired.
MacGyver suggests they move it to the subbasement to contain the blast. Professor Ryman uses liquid nitrogen to try and freeze the mercury while MacGyver props the elevator door open. However, the mercury is too far down in the bomb to freeze. David tells them there’s no way to disarm the bomb. MacGyver grabs a swivel stool and they very slowly place the bomb on it and start wheeling it toward the elevator. They get it inside but accidentally knock out the door jam. With 55 seconds left, they have to defuse the bomb. When Professor Ryman talks about pressure, MacGyver realizes that he can use gas pressure by heating the switch. MacGyver opens the elevator controls and runs two wires into the case. He puts one wire on either side of the mercury, heating the mercury and destroying the switch just in time.
The EMTs take David away and Professor Ryman goes with him. Janet comes over and MacGyver says it’ll take time for David to recover, and Professor Ryman promises he’ll make the time. As he leaves, Professor Ryman thanks MacGyver for his help.