When Lucy discovers that Ethel Merman and Mr. Mooney made up a story to hid the singer's real identity, she can't help but come up with the nerve to as Ethel to perform at her son's boy scout pageant. Ethel accepts and she does the show, along with Lucy and Mr. Mooney.

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.