Two giant dinosaurs appear and wreak havoc in San Francisco.
The Volcano Monsters was originally going to be distributed in the United States by Harry Rybnick and Edward Barison. The film was going to be even less true to Raids Again than Gigantis, the Fire Monster. All scenes with Japanese actors were going to be cut along with everything Gigantis took out, including neither Godzilla nor Anguirus breathing any type of fire and the two monsters just being giant dinosaurs. Toho still went ahead with the project as they wanted their films to be distributed in the United States in some way and they sent the GyakushuGoji and ShodaiAngira suits for the Americans to make new scenes with. However, The Volcano Monsters was never made because in July of 1957, the company Harry Rybnick and Edward Barison owned closed down and the suits were lost.
Eventually, the The Volcano Monsters project was replaced with Gigantis, the Fire Monster and the finished film ended up being distributed by Warner Bros.