The film flashes back to events occurring a year earlier in Zarpa Mesa. Famous scientist Leland Masterson (Harmon Stevens) arrives, having accepted an invitation from a fellow scientist named Dr. Aranya (Jackie Coogan). Aranya (name derived from the Spanish "araña" for spider) has reportedly penned "brilliant" scientific treatises, and Masterson looks forward to meeting him in person. Masterson is genuinely intrigued by Aranya's theories, but his host informs Masterson that his work is not theoretical. He has already completed successful experiments creating both human-sized tarantula spiders and human women with the abilities and instincts of spiders. His creation Tarantella has regenerative abilities sufficient to regrow severed limbs. He seriously expects her to have a lifespan of several centuries. His experiments have had less success in male humans, who simply turn to disfigured dwarfs.