Long ago, a terrible war between the ancient Mutors and the violent Inhumanoids raged far beneath the surface of the Earth. The mighty Redwoods and peaceful Granites and their allies fought against the Inhumanoids and defeated them against almost impossible odds. They drove the Inhumanoids into submission and sealed them away, until they were accidentally released by humans. They awaken and emerge from the fiery depths of the Earth and begin destroying everything in their path. The Earth Corps, with its top scientists, works to stop them.

The original miniseries that introduced the series was titled "The Evil That Lies Within", in which Earth Corps unveils a major archaeological discovery of a massive dinosaur-like creature encased and preserved in amber. The creature breaks loose and begins to wreak havoc, joined by others from among the ancient creatures. All episodes aired as part of Marvel's "Super Sunday" series. The brave members of the Earth Corp are their leader Herc Armstrong, advanced technology designer Dr. Derek Bright, specialized suit and vehicle designer and archaeologist Ed Augutter (aka "Auger"), and master of chemistry and various arcane sciences Jonathan Slattery (aka "Liquidator").