When a small Illinois town vanishes off the map in a single night, IntrepidReporter Audrey Aimes (Peggie Castle) swoops in smelling a scoop. Denied this, she begins investigating the goings on, leading her to Dr. Ed Wainwright (Creator/PeterGraves), who has developed a greenhouse full of [[ILoveNuclearPower atomic-sized fruits and vegetables]][[note]]By which we mean vegetables grown to enormous size through the use of atomic power, ''not'' [[IThoughtItMeant vegetables the size of atoms]][[/note]] -- which the local insect population keeps breaking into.

Continuing the investigation, Audrey and Peter eventually discover the culprit: LOCUSTS! BIG ONES!! Irradiated by the good doctor's atomic plants, the local locust population has been transformed into a NighInvulnerable swarm of eight-foot-plus bugs [[DoomyDoomsOfDoom of DOOM!]] The giant bugs begin chowing down on ([[SpecialEffectsFailure postcards of]]) the Illinois countryside and work their way toward UsefulNotes/{{Chicago}} while Dr. Wainwright tries to figure out how to stop them.

For the ''Series/MysteryScienceTheater3000'' version, please go to the [[Recap/MysteryScienceTheater3000S05E17BeginningOfTheEnd episode recap page]].

!!''Beginning Of The End'' provides examples of:

* ArtisticLicenseGeography: The locust swarm goes from Rantoul to Chicago ... by way of Peoria (making a substantial detour to the west, for those who don't have a map of Illinois handy).
** Also, the infamous "suburbs of Paxton." Paxton, Illinois, is a small rural town (population slightly under 4,500 as of 2010) which has never had suburbs. They might have meant it was "suburb of Paxton".
* AttackOfThe50FootWhatever: Actually, [[YourSizeMayVary the script mentions that the Big Bugs come in various sizes]], in an effort to cover the lousy compositing work.
* AutoErotica: The couple in the ColdOpen only manage to get to first base before they're killed off though.
* BigCreepyCrawlies: The locusts, of course.
* {{Chickification}}: Audrey Aimes goes from IntrepidReporter in the first half of the movie to NeutralFemale in the latter half.
* GiantFood: Subverted; Wainwright's bowling-ball-sized strawberries and other oversized produce aren't safe for human consumption.
* GodzillaThreshold: The Army is willing to ''nuke Chicago'' to stop the locusts.
* MoreDakka: When Wainwright gets his hands on a military submachinegun.
* TheMountainsOfIllinois: The TropeNamer!
* PoliceAreUseless: Audrey invokes this to justify her continued investigation into things: "The sheriff thinks in terms of 'crime and publicity'. You're a ''scientist''; you think in terms of 'cause and effect'; maybe [[TheOnlyOne you'll see something the sheriff missed]]."
* RealLifeWritesThePlot: A rather creepy example, as we see fewer and fewer locusts onscreen at once as the film goes on, as they had started ''eating each other''.
* {{Retirony}}: "You know, I'm 37 years old, and I've [[TemptingFate just realized how much I've taken life for granted]]."
* TheSpeechless: Deaf/mute Frank.
* TitleDrop: "Annihilation... the beginning of the end."
* YouHaveToBelieveMe: Played hilariously straight even as Dr. Wainwright intones, "You know I'm not given to hysteria and you've got to listen to me with an open mind!"
** It doesn't help that Audrey [[IdiotBall fails to take a photograph of the giant locust]] when she has the chance.
** At least Ed gets in the one response most others in his situation never think of: "Won't you at least check it out? ''Or have you'' '''''found''''' ''an answer?''"