LitCharts assigns a color and icon to each theme in The Alchemist, which you can use to track the themes throughout the work.
Alchemy and Transformation
Religion
Sex and Greed
Deception and Gullibility
Summary
Analysis
Lovewit knocks on the door again, and Face answers as Jeremy the butler, his face shaved clean. “O, here’s Jeremy,” the neighbors say. Lovewit asks Face where he has been and what is going on. Face tells Lovewit that the house was hit with the plague. Weeks ago, he noticed the cat displaying symptoms and thought it best to close up the house. He locked up and left, and he has only just returned. But, Lovewit says, the neighbors witnessed many men and women coming and going these past few weeks. Face insists that he was gone and asks the neighbors if they saw him recently. No, they say, and Jeremy “is a very honest fellow.”
Again, Lovewit’s neighbors are extremely gullible and don’t recognize him at all. Jeremy, of course, is not “a very honest fellow.” It may seem like a sick cat is far-fetched and Lovewit is just as gullible; however, the plague was carried by fleas and rodents, so it is certainly plausible that a cat could come down with the plague and potentially infect the whole house if not quarantined.