...where the sewer connects with the riverfront

Basil:
[Regarding Fidget's note]
Offhand I can deduce very little, Only that the words are written with a broad-tip quill pen that has spattered, twice; that the paper is of native Mongolia manufacture, no watermark; and has [smacks his lips against the paper] Basil:
been gummed, if I'm very much in error... [smells paper] Basil:
...by a bat who has been drinking Rodent's Delight, a cheap brandy served only in the seediests pubs. Dr. Dawson:
Hmm. Amazing. Basil:
Oh, not really, doctor. We still don't know where it came from. Perhaps a closer inspection will tell us something. [Looks at note under microscope] Basil:
Coal dust, clearly of the type used in sewer lamps. [Takes note and sets it on fire] Dr. Dawson:
Basil! Basil:
Shh. Don't speak. [He grinds the ashes in a crucible and pours them into a beaker] Basil:
Excuse me, Doctor. [Takes beaker and a bottle of liquid] Basil:
Steady hand... [pours a drop into beaker and sets it at the other end of a pipe; he boils a liquid on the other end, watching as it goes through the pipe] Basil:
Come on, come on. Good, bad, bad, good. Come on, Come on, come on. [Liquid finally reaches beaker; chemical explodes] Basil:
Aha! We've done it, old fellow! This chemical reaction could only be triggered by the paper's extreme saturation with distilation of sodium chloride. Dr. Dawson:
Salt water? Great Scott. Basil:
It proves beyond a shadow of a doubt, this note came from the riverfront area. [Pins a map of the river on the wall] Dr. Dawson:
Now, steady on, Basil... Basil:
No, it's elementary, Dawson. We simply look for a seedy pub at the only spot... [Pins dart on map] Basil:
...where the sewer connects with the riverfront