AstheShaneGangreturntothe99cavernsfromtheirEasternadventure,adisputeeruptsbetweenthemandtheShadowClan,threateningtoshatterthehard-wonpeaceinSlugterra.EliandtheGanghavetheirhandsfulldealingwiththeanticsoftheusualthugs,plusgrowinghostilityfromtheirformerallies.SowhenTadandhisslugPieper-whohavejustarrivedfromtheSurface-lendahandwithPieper'samazingpowers,Eliwelcomesanewteammember.Butsoonthisnewcomercastshisownshadowonthechaos.