Northumberland: the winter of 1937. In a remote moorland cottage, Steven Coulter, a young history teacher, is filled with sadness and longing at the death of his wife. Through a charismatic colleague, Frank Embleton, and Frank's sister, Diana, he is drawn into the beguiling world of a group of musicians, and falls gradually under their spell. But as war approaches a decision is made which calls all their lives quite shockingly into question.

Moving between the beauty and isolation of the moors, a hill-town school and a graceful old country house, Trio delicately explores conscience and idealism, romantic love and most painful desire. Throughout it all, the power of music to disturb, uplift and affirm is unforgettably evoked.