the mu empire executes a devastating attack on tokyo and threatens to sacrifice its prisoners to the monstrous deity manda if "atragon" appears. appear the super-submarine does, pursuing a mu submarine to the empire's entrance in the ocean depths. meanwhile, susumu and the other prisoners escape their cell and kidnap the empress of mu. they are impeded by manda, but soon rescued by "atragon", which then engages the serpent and freezes it using the "absolute zero cannon". jinguji offers to hear peace terms, but the proud empress refuses. the captain then advances "atragon" into the heart of the empire power room and freezes its geothermal machinery. this results in a cataclysmic explosion visible even to those on deck of the surfaced submarine. her empire dying, the mu empress abandons the "atragon" and, jinguji and company looking on, swims into the conflagration.