"The Stolen Bacillus" is a short satire that focuses on the role of science in human society, making it thematically similar to many of Wells' other works. The story begins with a bacteriologist and his anxious yet intellectually curious houseguest. Upon request, the scientist shows his guest a vial of living cholera bacteria, and the vial is stolen shortly after the man's departure. The bacteriologist goes on a panicked search when he realizes his houseguest is actually an anarchist who plans to infect London's water supply with cholera.
As the bacteriologist pursues his target, he is in turn pursued by his wife, who thinks he has lost his mind since he ran out of the house without being properly dressed. The bacteriologist finally catches up with the anarchist, who breaks the vial in an attempt to escape. In a desperate effort to bring his menacing plan to fruition, the man drinks the remains of the vial's contents and begins his effort to infect the city with cholera on his own.
As the story comes to a close, the bacteriologist informs his perplexed wife that what was in the vial was not actually cholera. Suspicious of the guest's intentions, the scientist showed him a vial that contained a new microbe that would turn an animal's skin blue. After revealing this twist, he grudgingly returns home with his wife to begin working on a new culture of the strange microbe.
In summary, this story uses irony to tell the tale of a clever scientist and an impulsive anarchist who become involved in a horse-drawn cab chase over a substance that is not at all what it seems. Wells uses this work to discuss the potential role science plays in the facilitation of bioterrorism.