When the villain known as the Kangaroo steals a vial of experimental bacteria, Spider-Man swings into action to save the day.
Spider-Man is web-swinging swiftly through Manhattan, determined to reach the train station so that he can meet Aunt May. When he gets there, Aunt May assumes he is sick, since his face is flustered from web-swinging so much, and demands that he stay at her house for the night. Just a few meters from Peter and Aunt May is a criminal called the Kangaroo, who has to be deported. Before the police can put handcuffs on the Kangaroo, however, he manages to knock them down then escape by leaping over the crowd.
The Kangaroo's mind then flashes back to all the time he spent in Australia, studying kangaroos. After months of training in the wilderness where the kangaroos were, the Kangaroo cashed in on his power in boxing. However, his extraordinary kicking abilities severely hurt his opponent, and the Kangaroo had to flee so that charges weren't pressed against him. He managed to stow away to America, but was found by the police and put on a train to New York.
Meanwhile, at Aunt May's house, Aunt May puts Peter into bed, worried about his health. Although Peter is perfectly fine, he puts up with it anyway, since he knows it will make Aunt May happier.
Somewhere in New York, three guards are guarding a vial containing a deadly bacteria. The Kangaroo notices them, and assumes the vial they're guarding to be something valuable. Upon attacking the guards, the Kangaroo opens up the case the vial was in and finds the vial. Assuming it to hold jewels, the Kangaroo angrily puts it away, as he needs money.
At Aunt May's house, Peter and Aunt May see a news bulletin explaining about the theft, and what could happen if the vial were opened. Peter puts a web dummy in his bed, so that it will appear he's still there, before swinging off to find the Kangaroo.
After searching for hours, Peter finally finds the Kangaroo, who is trying to threaten people into giving him their money. Although Spider-Man could easily defeat him, he can't risk hitting the Kangaroo too hard, as he might break the vial. After a bit of dodging Kangaroo's blows, Spider-Man realises he can shake the vial out of Kangaroo's jacket, and gives it to the police whilst Kangaroo gets away.
Upon returning home, Peter finds that Aunt May had found the web dummy, and fainted. He throws it away, then wakes Aunt May up, although the only way he can convince her that he was there all along was by getting her to think that she's senile.