Threesome in a dim dungeon with the hired helper

A couple hires a shampoo girl, turning a routine wash into a bold, explicit scene in a dim dungeon. The dominant mistress undresses the blonde and has her ride a bound sub, then the pair switch so the shampoo girl takes her turn. When the cuffs come off, the bound sub pleases them in new positions, and the man cums on the blonde's tits.