Professor Farnsworth announces that tomorrow the crew will make a delivery to Ebola 9, the virus planet. They cannot go today because he wants them all to be alive for the Academy of Inventors annual symposium, where he will present the Deathclock, a device which calculates how long a person has left to live. At the symposium, he meets a former student of his from Mars University, Professor Ogden Wernstrom, who vowed revenge on the Professor after receiving an A-minus on a pop quiz, even if it took him a hundred years. Just over ninety-nine years have passed, and no revenge is in sight; so Farnsworth considers himself to be in the clear.
Wernstrom presents his invention, an apparatus that allows fish to breathe water, but travel on land. He taunts Farnsworth over his invention from the previous year-the Deathclock. Mortified that he had already presented the invention and forgotten about it, Farnsworth hastily begins drawing on a napkin, and comes up with the smelloscope, a device that allows people to smell distant cosmic objects. The smelloscope is received with scorn and laughter, and Wernstrom gives it "the worst grade imaginable-an A minus minus".
Back at Planet Express, he invites everybody to see the smelloscope which he already built last year and also forgot about. Fry begins pointing the smelloscope around, and discovers the smelliest object in the universe. After calculating its path, Professor Farnsworth announces that the object will collide with New New York City in 72 hours. After some research, a video is found, revealing the object to be a giant ball of New York City's garbage launched via mob-obtained rocket into space around 2052 in an attempt to alleviate a crippling rubbish problem.
After warning the mayor of New New York, Mayor Poopenmayer, a plan is hatched to destroy the garbage ball. The Planet Express crew is sent on a mission to plant a bomb on a fault line on the ball. The bomb has been set to allow twenty-five minutes to escape. When the crew lands on the ball, Fry is amazed of all of the 20th–century items on the ball; but Leela reminds Fry that these things were garbage, which is why they are in the garbage ball in the first place. Unfortunately, the Professor put the bomb's countdown display in upside down, and it actually only allows fifty-two seconds. The crew panics, and Bender throws the bomb into space to save themselves, but runs into a small meteor and falls back to the surface; and Bender throws it again. The opportunity to destroy the garbage ball is lost, so the crew returns to Earth in shame.
Attempting to find another way to save the city, the Mayor sends in Wernstrom to find a way to stop the garbage ball. Wernstrom demands tenure, a grant, and five scientists, but has no plan, declares that he's set for life, and leaves. In a last-ditch effort to redeem himself, Farnsworth comes up with a second plan to save the city: to launch a second ball of garbage to bounce against the first one to send it flying into the sun. The Mayor exclaims that there hasn't been garbage in New New York for 500 years, so Fry demonstrates how to make garbage. An announcement is made to tell the city to not throw away its garbage. The city of New New York quickly generates a second ball of garbage, which is fired at the first garbage ball. The rocket flies into the air and hits the other garbage ball head-on. The second ball of garbage flies out of the solar system and the other flies into the sun. Leela's concerns that the new garbage ball will return and destroy a future generation are dismissed by other characters. Fry says that it won't be for hundreds of years.