Gaira, a humanoid sea beast spawned from the discarded cells of Frankenstein’s monster, attacks the shores of Tokyo. While the Japanese military prepares to take action, Gaira’s Gargantua brother, Sanda, descends from the mountains to defend his kin. A battle between good and evil ensues, leaving brothers divided and a city in ruins.

San Francisco businessman Harry Graham and his wife and business partner, Eve, are in the process of adopting a child. Private investigator Mr. Jordan uncovers the fact that Graham has another wife, Phyllis, and a small child in Los Angeles,