Black is the colour of my true-love's heart

Singers and musicians are gathered for a course in folk music that will occupy a weekend in the fantastic country mansion called Follymead. Most come only to sing or to listen, but one or two have non-musical scores to settle. When brilliantly talented Liri Palmer sings "Black, black, black is the color of my true-love's heart!" she clearly has a message for someone in the audience. Passions run high, and there is murder brewing at Follymead.