By 1964, ten years after the release of the original Godzilla, it was clear that tokusatsu films were here to stay. What's more, Toho was clearly the leader of the pack with its growing retinue of kaiju, from the King of Monsters himself to lesser known beasts like Varan. Looking at the success of their crossover hit, Mothra vs. Godzilla, it's little surprise that Toho decided to go one better, and combine their three most popular kaiju in a single film. That film was Ghidorah, the Three-Headed Monster.
If Mothra vs. Godzilla was the first film to directly reference a shared continuity between Toho's tokusatsu films, Ghidorah firmly established it once and for all. A direct sequel to Mothra vs. Godzilla, Ghidorah not only reunited Godzilla and Mothra, but brought Rodan into the mix as well and pitted all three against a single foe, more powerful than any of them. In a way, Ghidorah is Toho's equivalent to the The Avengers: a crossover featuring a team-up of the company's most popular characters in a battle to save the world. The analogy isn't perfect, but I think it captures what would, in retrospect, prove one of Toho's most significant films.
The film opens in January of 1964, as a group of UFO enthusiasts watch the sky for signs of extraterrestrial intelligence. Reporter Naoko Shindo is skeptical that they'll find anything, despite several recent and unusual occurrences, such as a heat wave in the middle of winter. As Naoko interviews the group, one of them spots what they believe to be a flying saucer, although it turns out instead to be the first in a series of meteors.
Around the same time Naoko's detective brother is assigned to protect Princess Maas Doulina Salno of Selgina, during her unofficial visit to Japan. Selgina (an apparent analog to Nepal) is in political turmoil and there is reasons to suspect the princess' life is in danger, for which reason Shindo has been hired. Before he is able to take up the job, however, Princess Salno's plane explodes en route to Japan. The Princess escapes just in time, however, with the help of a mysterious intelligence that contacts her in the form of a bright light and warns her of the impending explosion.
Meanwhile, some distance away, one of the meteors falling to Earth crashes into the mountains near Kurobe. Professor Murai, from the Teito Institute of Technology (not to be confused with Professor Miura from Mothra vs. Godzilla, both played by Hiroshi Koizumi) arrives shortly thereafter, intent on investigating the impact site. On their way over the mountains, Murai and his team discover the meteor is emitting an intense magnetic field, which is affecting their compasses. Their surprise increases when, at the impact site, their metal tools fly away from them, likewise affected by the magnetic field. Curious, the group sets up camp to study the meteorite in more detail.
Later, Naoko, turning away from her story on the astronomers, picks up a new story when her editor Kanamaki informs her that a doomsday prophet has appeared in Ueno Park. Naoko heads to the site immediately, where a crowd is ridiculing and harassing the prophet, who claims to be from the planet Venus. In order to establish her credibility, the prophet predicts a disaster at Mount Aso in Kyushu.
While the world waits to see if these predictions come true, Naoko and her brother return home for dinner. After discussing Naoko's budding friendship with Professor Murai, the two siblings and their mother turn on the television to watch a variety show, which has secured the Shobijin of Infant Island as special guests. The two women, now bona fide celebrities after the events of Mothra vs. Godzilla fill their hosts in on the condition of Infant Island and the Mothra twins, one of whom has passed away. Bored with the program, Shindo looks at the day's newspaper and sees the Venusian prophet, who he immediately recognizes as Princess Salno. In Selgina, the conspirators come to the same conclusion and send their chief assassin, Malness, to kill her.
After disappearing from the public eye briefly, the prophet reappears at Mount Aso. There, she warns the public that one of the Rodan twins buried eight years later is about to reemerge. Sure enough, the flying monster emerges just a few minutes later, vindicating the prophet's claims. As a result, when she makes her second prediction, claiming that a passenger vessel will be destroyed at sea, some people, such as the Shobijin, take her more seriously. Later that night, the second prediction comes true as well, when Godzilla emerges from the sea to attack the ship en route to its destination, sinking it.
With her credibility firmly establishes, the Venusian makes one final prediction: King Ghidorah, the alien destroyer of worlds, will appear and lay waste to Earth as he did her own home. With Godzilla and Rodan converging on Kurobe and a third threat immediately imminent, the Japanese government calls on Mothra once more to aid them. The Shobijin agree to send for her, but are concerned that the larval Mothra is not strong enough to defeat Godzilla and Rodan on its own, let alone a third monster. Desperate, Mothra tries to persuade Godzilla and Rodan to put aside their hatred for humanity in order to save the planet from King Ghidorah.
The film, which was directed by series mainstay Ishiro Honda and written by Shinichi Sekizawa, is an important part of the Showa canon in many respects. Among other firsts (such as the premiere of Godzilla's most iconic foe), Ghidorah is the first Toho film to directly state that kaiju are sapients capable of complex thought and communication. Mothra's appeal to Godzilla and Rodan would be meaningless if neither were capable of rational decision-making. The Shobijin even translate the conversation into Japanese, providing an explanation for Godzilla and Rodan's motives for their attacks on humanity.
Relatedly, Ghidorah is the turnaround point for Godzilla, transforming him from a villain into a protagonist. In previous films, Godzilla had always been humanity's enemy; a force of destruction which served as a dark allegory for both Japan's devastation during World War II and nuclear weapons more specifically. In Ghidorah, however, Godzilla becomes (somewhat reluctanly) humanity's ally, which would remain the status quo for the rest of the Showa series.
Altogether I enjoyed Ghidorah, the Three-Headed Monster quite a bit. The story is surprisingly layered for what is essentially just an excuse to throw Toho's three most popular monsters together and the special effects are a marked improvement in some ways (the Shobijin in particular are a little more convincing here than in previous films). The final showdown between Godzilla, Mothra, Rodan, and King Ghidorah is one of the best monster fights in the Showa series. Big intra-franchise crossovers like Ghidorah don't always work, but when they do, they're definitely something special.