Deep inside the Earth exists the vast underground world of Slugterra, named after the tiny slugs who live there. The Shane family are the traditional guardians of Slugterra and have kept its existence secret from the world as they train the slugs for use as living ammunition. A threat appears in the form of Dr. Thaddeus Blakk, who wants to transform the Slugs into evil weapons he calls "ghouls." 15-year-old Eli Shane must take his place as the new guardian of Slugterra and, with the help of the slugs and his gang, stop Dr. Blakk.