We are dealing with an exceptionally astute and dangerous man… one of the most unscrupulous rascals that Australia has ever evolved—and for a young country it has turned out some very finished types.

In this remark, Conan Doyle frames his subject as a rare blend of intelligence and moral vacancy: “astute and dangerous” suggests strategic brilliance turned toward predation rather than achievement. The phrase “unscrupulous rascals” intensifies the ethical judgment, implying a person who treats rules, loyalties, and human costs as disposable. The closing barb—Australia as a “young country” that has nonetheless produced “very finished types”—adds a colonial-era note of sardonic surprise, implying that sophistication in criminality can develop quickly in new societies. Overall, the line functions as a warning: the most serious threats come not from crude violence but from capable minds unrestrained by conscience.