▁becomes ▁part ▁of ▁the ▁group ▁in ▁The ▁Myst ery ▁of ▁the ▁Cl uel ess ▁Cor pse . ▁Tony ▁has ▁not ▁appeared ▁since ▁The ▁Myst ery ▁of ▁the ▁Mur der ed ▁Ma id ▁when ▁he ▁went ▁back ▁to ▁America , ▁meaning ▁that ▁he ▁might ▁have ▁left ▁the ▁group ▁perman ently . ▁Ar pe eta : ▁Ar pe eta ▁is ▁Sin ch ita ' s ▁little ▁sister ▁and ▁has ▁waited ▁a ▁long ▁time ▁to ▁join ▁Al vin ' s ▁group ▁of ▁investig ators . ▁She ▁first ▁appears , ▁and ▁becomes ▁part ▁of ▁the ▁group ▁in ▁The ▁Myst ery ▁of ▁the ▁C low n ish ▁Cor pse . ▁She ▁is ▁shown ▁to ▁have ▁a ▁good ▁singing ▁voice ▁( The ▁Myst ery ▁of ▁the ▁Christmas ▁Carol ), ▁and ▁also ▁writes ▁poetry ▁( The ▁Myst ery ▁of ▁the ▁B other ed ▁Bro ther ). ▁ ▁Minor ▁characters ▁Serge ant ▁So o : ▁His ▁name ▁is ▁Samuel ▁So o . ▁He ▁was ▁friends ▁with ▁Alan ▁So h , ▁Al vin ' s ▁father . ▁Serge ant ▁So o ▁always ▁helps ▁Al vin ▁in ▁his ▁investig ations , ▁whether ▁he ▁lik es ▁it ▁or ▁not . ▁He ▁became ▁protect ive ▁towards ▁Al vin ▁and ▁his ▁team ▁after ▁he ▁learned ▁that ▁Alan ▁So h , ▁Al vin ' s ▁father , ▁was ▁murder ed ▁by ▁The ▁S nake . ▁He ▁has ▁a ▁rom antic ▁relationship ▁with ▁G rac ie ▁So h . ▁He ▁later ▁becomes ▁extremely ▁protect ive ▁towards ▁Al vin ▁and ▁forb ids ▁the ▁team ▁to ▁be ▁involved ▁in ▁any