Pollution is continually worsening. Scientist Yano examines a very strange looking fish that looks like a giant tadpole. He has a collection of other strange looking fish that have been preserved on his shelves. Meanwhile, some sort of beast attacks fishing vessels in the Sea of Japan. It has a strange resemblance to the odd fish brought to Dr. Yano earlier. Dr. Yano goes skindiving near the attack to look for evidence. Instead, he finds the ocean floor littered with trash. On shore, Ken discovers the oysters have no meat in them and that dead sea creatures are in the wash. Suddenly, the giant tadpole with blazing red eyes leaps out of the water and flies over him! Yano and the giant tadpole meet underwater. Later that day, Dr Yano is bedridden from the attack, gravely injured with an ugly grey wound across half his face. Ken has named the beast “Hedorah.”
Following a trail of pollution, Hedora crawls ashore. It finds a pair of smokestacks and breaths in the noxious fumes, growing even larger. Godzilla, who Ken has speculated is frustrated and angry about the pollution, confronts Hedorah. The polluted beast leaps at Godzilla. Hedorah’s own horrible odor brings down the King of the Monsters. As they continue to grapple, Godzilla is able to bring himself back up and swings Hedorah around, splashing muck everywhere. Godzilla eventually flings away Hedorah. He uses his nuclear breath against the creature, which flees to the ocean. Godzilla gives chase, but cannot find the other monster.
Once in the ocean, Hedorah regains strength, and the ability to fly. After some forensic testing, Dr Yano realizes the Hedorah is mineral, not animal. He suspects it arrived on Earth in a meteor and the pollution caused it to grow. It also creates sulfuric acid as a deadly, corrosive smog.
Hedorah reappears in the skies above Japan. Where it flies, people collapse from the noxious fumes it emits. If they have direct contact with the toxic mist, they dissolve to skeletons.
Using a tiny piece of Hedorah, Dr. Yano finds that an electrical shock can dry out and destroy the polluted beast. Meanwhile, a group of young adults has gathered at Mount Fuji to protest pollution and celebrate life at the same time.
Hedorah continues its path of destruction toward Mount Fuji. Godzilla is there and steers the monster away from the partygoers. As the two beasts face each other, Dr. Yano finds out the giant electrodes the humans plan to destroy Hedorah with are not yet finished. Hedorah knocks Godzilla to the ground and advances towards the partiers. They throw torches at the creature, but they are nothing more than matchsticks. Hedorah emits its noxious fumes, killing many of them. As it moves to kill those remaining, Godzilla fires a nuclear blast ahead of Hedorah, distracting it.
The two wrestle, but Hedorah’s deadly fumes overpower the King of the Monsters. Hedorah carries Godzilla to Mount Fuji, drops him into a crevice, and oozes nasty polluted muck into the crevice. Godzilla appears doomed. Can the military set up the electrodes before Hedorah destroys he world?
As the Army Commander discusses the plan with the still injured Dr Yano. Godzilla and Hedorah continue their struggle, falling down the side of Mount Fuji and crashing into the power lines! The Commander orders new lines installed quickly.
By this time, Hedorah is larger than Godzilla, and is getting the upper hand in the continuing battle. Godzilla lies wounded and Hedorah leaves the battlefield toward the still non-functioning electrodes. Trying to keep the monster near, the solders blink their headlights. It moves closer to the headlights and the soldiers, but there is still no power. Everyone is waiting for the coming death.
A nuclear blast activates the electrodes! Godzilla has energized the devices. He fires another blast and the electrodes dry Hedorah out, causing it collapse. Godzilla shoves his hand inside and pulls out two shiny globes. He again activates the electrodes, vaporizing the globe/hearts. A smaller Hedorah emerges from the remains of the other and flies off. Godzilla uses his nuclear breath as a jet and flies backwards to the escaping Hedorah. But the smaller, weaker Hedorah is no match for a rejuvenated King of the Monsters. Godzilla grabs the monster and he flies them back to the electrodes, which have new powerlines attached. The humans turn on the juice, but it’s not enough. Godzilla uses his nuclear breath again to reactivate the electrodes, finally causing Hedorah to shrivel up. Godzilla rips the guts out of Hedorah. Before the guts can become new Hedorahs, he activates the electrodes and shrivels them up.
Godzilla turns and leaves. He is angry, however. He may have defeated Hedorah, but pollution is still destroying the world.
Human Cast: Akira Yamauchi (Dr. Yano), Hiroyuki Kawase (Ken Yano), Toshie Kimura (Toshio Yano), Keiko Mari (Gara Takatori), Toshio Shibamoto (Yukio Keuchi)
Monster Cast: Godzilla, Hedorah
Notes: The opening title sequence is obviously inspired by Maurice Binder’s title sequences for the James Bond movies. The movie’s original title was Godzilla Vs. Hedorah; when imported to North America, the distributor renamed this movie Godzilla Vs. The Smog Monster, and replaced the theme song with the English language song “Save The Earth.” Since then, the “commonly available” version that usually airs on TV and is now on DVD has restored the original title and the Japanese language theme song. However, Godzilla Vs. The Smog Monster is readily available on an apparently properly licensed disc that is packaged with Godzilla Vs. Megalon.
LogBook entry by Robert Parson