 Dennis Potter s contribution to  The Sextet , a series of six BBC television plays on sexual themes.  Follow the Yellow Brick Road  tells the story of actor Jack Black, who specialises in commercials because they are untouched by what he sees as the grime of the real world. Estranged from his wife, who he caught in bed with another man, his idea of purity is his agent s child-like wife. He is to be disappointed; his frustration with the world s dirt leads him into bitter confrontation with the medical consultants who try to reach the heart of his problem, and his wife, who would have a reconciliation.