▁The ▁Syl ph ▁is ▁an ▁ep istol ary ▁novel . ▁It ▁cent res ▁on ▁Julia ▁Gren ville , ▁a ▁Wel sh ▁beauty ▁and ▁ingen ue ▁( with ▁whom ▁there ▁are ▁par alle ls ▁with ▁Cav end ish ▁herself ) ▁who ▁leaves ▁her ▁id yl lic ▁rust ic ▁life ▁to ▁marry ▁a ▁rich ▁member ▁of ▁the ▁arist ocracy . ▁Over ▁the ▁course ▁of ▁time ▁she ▁un co vers ▁the ▁fact ▁that ▁her ▁husband ▁is ▁a ▁ra ke ▁and ▁a ▁libert ine , ▁lav ishing ▁his ▁wealth ▁on ▁g amb ling ▁and ▁mist ress es . ▁The ▁letters ▁are ▁chief ly ▁written ▁to ▁her ▁sister s ▁and ▁provide ▁narr ative ▁detail ▁about ▁Julia ' s ▁life ▁in ▁London ▁and ▁her ▁dis ill usion ment ▁with ▁the ▁m ores ▁of ▁the ▁inhabitants ▁of ▁the ▁city ▁as ▁well ▁as ▁her ▁mis car riage . ▁We ▁also ▁discover ▁that ▁she ▁has ▁a ▁long - term ▁adm ir er , ▁Henry ▁Wood ley , ▁that ▁she ▁has ▁growing ▁aff e ctions ▁for ▁another ▁man ▁( the ▁Baron ▁Ton - hausen ) ▁and ▁also ▁that ▁she ▁has ▁a ▁myster ious ▁and ▁en ig m atic ▁prote ctor ▁and ▁guard ian , ▁who ▁is ▁the ▁' s yl ph ' ▁of ▁the ▁title . ▁The ▁s yl ph ▁helps ▁provide ▁advice ▁to ▁Julia ▁on ▁the ▁way ▁to ▁negoti ate ▁the ▁lab yr inth ▁of ▁metropol itan ▁high ▁society , ▁appearing ▁in ▁the ▁work ▁only ▁in ▁the ▁double ▁fict ional ▁form ▁of ▁a ▁mas qu erade . ▁ ▁Event ually ▁Julia '