Dr. Bradley Shaw and his manipulative assistant Penny study Spider-Man and his powers carefully, with the intent to duplicate them for their own purposes. After obtaining a sample of Spider-Man's blood, they discover that the catalyst for his powers was radiation. In the meantime, Peter uses any excuse possible to avoid giving blood at the Bugle, since his blood contains the aforementioned radioactive elements. Penny forces Shaw to experiment on himself, to give him the powers of Spider-Man. She allows him to receive an overdose of radiation in addition to an injection of spider D.N.A., and instead of simply duplicating Spidey's powers, he is turned into a half-human half-spider mutation known as Nephilia. He goes to the Bugle and webs up Jameson to get Spider-Man's attention. Soon, the two spider-men meet up and clash with each other. Spidey finds out that a nephilia spider was sold to Dr. Shaw and goes to his workplace, where he finds a message from Penny telling him that she and Nephilia will rob an armored shipment of gold. It falls to Spidey to protect the shipment of gold and find a cure to return Dr. Shaw to normal, as well as fooling Jameson that he has in fact donated some blood.

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The design of Nephilia and the general plot of this episode were both reused in the third season (1983) episode of Spider-Man And His Amazing Friends entitled "Attack Of The Arachnoid".

- In a scene in a library there is a book on the shelf entitled "How To Identify Spiders" by Roy Wilson. Roy Wilson was one of the layout artists, and presumably this was an in-joke on his part.