Holmes concludes that his dark visitor is nothing to do with London, or England, or indeed anything he knows; the stranger's poetry is incomprehensible, his manner is odd, and his fascination with the rivers of London is puzzling.
However, Mr Gouen's request, concerning the recovery of a family scroll, is straightforward enough. Holmes understands crime; he understands conspiracy; he understands how to follow the trail through London and obtain the scroll and finally bring the criminals to justice.
Mr Gouen leaves him with a poem, which Holmes keeps, but which he does not read again after the first baffled comprehension.
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