Sunshine and Sinthia are step-sisters. Sunshine has been away from home for a long time and Sinthia invites her to a meeting to discuss their step-father's inheritance.
According to the document that Sinthia has, only one of them will get the inheritance and they have to compete for it. The contract says that one of them must be able to get out of bondage before the other can to win the inheritance. Sinthia and Sunshine are hogtied and their mouths are stuffed with large ballgags.
Eventually Sinthia gets out of her hogtie and reveals that she was able to get out of it because she rigged it from the start and that there was no inheritance. It was all a trick to get Sunshine back home as Sinthia has been craving her feet for many years. Sunshine is understandably mad and struggles hard and tries to yell through her gag.
Sinthia rather than let her go, removes her flats and worships her feet. Eventually Sinthia decides that she shouldn't be having all the fun. Sinthia removes sunshines ballgag, removes her own flats, and makes Sunshine lick the insides of her flats while telling her she deserves it.