Final answer:
In the context of the passage from 'Hidden Gold' by Wilder Anthony, 'ingenuous' most likely means someone who is straightforward and simple.
Step-by-step explanation:
In the passage from “Hidden Gold” by Wilder Anthony, the term “ingenuous” is used to describe a man who is attempting to become a detective. Given the context in which Dorothy mocks Lem Trowbridge for his transparency and straightforwardness, it is suggestive that the term refers to someone who is straightforward and simple, rather than sophisticated, cunning, or dependable. The passage implies that Trowbridge lacks the deceit or complexity that might be associated with a trained detective like Sherlock Holmes, pointing towards a more innocent and open nature.