Brothersonwasunusuallyactiveandalertthatevening。Hewasanxioustofitonedelicatebitofmechanismintoanother，andhewascontinuallyinterruptedbyvisitors。Somebigeventwasoninthesocialisticworld，andhispresencewaseagerlydemandedbyonebrotherhoodafteranother。Sweetwater，postedathisloop-hole，heardtheargumentsadvancedbyeachseparatespokesman，followedbyBrotherson’sunvaryingreply：thatwhenhisworkwasdoneandhehadprovedhisrighttoapproachthemwithamessage，theymightlooktohearfromhimagain；butnotbefore。Hispatiencewasinexhaustible，butheshowedhimselfrelievedwhenthehourgrewtoolateforfurtherinterruption。Hebegantowhistle-atokenthatallwasgoingwellwithhim，andSweetwater，whohadcometounderstandsomeofhismoods，lookedforwardtoanhourortwoofcontinuousworkonBrotherson’spartandofdrearyandimpatientwaitingonhisown。But，assomanytimesbefore，hemisreadtheman。Earlierthancommon-muchearlier，infact，Mr。Brothersonlaiddownhistoolsandgavehimselfuptoarestlesspacingofthefloor。Thiswasnotusualwithhim。Nordidheoftenindulgehimselfinplayingonthepianoashedidto-night，beginningwithafewheavenlystrainsandendingwithabangthatmadethekey-boardjump。Certainlysomethingwasamissinthequarterwherepeacehadhithertoreignedundisturbed。Hadthedepthsbeguntoheave，orwerephysicalcausesaloneresponsiblefortheseunwontedebullitionsoffeeling?
Thequestionwasimmaterial。EitherwouldformanexcellentpreparationforthecoupplannedbySweetwater；andwhen，afteranotherhourofuncertainty，perfectsilencegreetedhimfromhisneighbour’sroom，hopehadsoaredagainonexultantwing，faraboveallformerdiscouragements。
Mr。Brotherson’sbedwasinaremotecornerfromtheloop-holemadebySweetwater；butinthestillnessnowpervadingthewholebuilding，thelattercouldhearhisevenbreathingverydistinctly。Hewasinadeepsleep。
Theyoungdetective’smomenthadcome。
Takingfromhisbreastasmallbox，heplaceditonashelfcloseagainstthepartition。Aninstantofquietlistening，thenhetouchedaspringinthesideoftheboxandlaidhisear，inhaste，tohisloop-hole。