If that detective was an insider who knows about the peculiarities of D'ni culture, I might agree. But we are talking about an outsider; how much of the D'ni magic would seem impossible to a Sherlock Holmes and therefore would be ignored? Personally, I prefer the hard-boiled detective type. They don...
If you're sure outside help will bring results. Call me a sourpuss but I have my doubts that they can catch our saboteurs faster than a nicely concealed bear-trap.