In order to wage germ warfare on Japan, Destron takes over the Osato Biological Institute and tortures the head scientist, to pillage his research. Meanwhile Rider Scout Yoshio notices that young women go into the institute but don't come out. So he snoops around to check things out, but is captured by Cockroach-Spike. Junko goes in to rescue him posing as a housekeeper, but is also caught spying. Can V3 thwart Destron's plot?