A summer at Glenvara in Ireland with her cousins gave Sheila O'Mara, a young British girl faced with a choice of vocations, the opportunity to persuade her father, a school principal in England, that writing offered good possibilities for a career. And Sheila's visit gave her cousin, Mairin, 17, the audience and encouragement she craved to further an acting career. The family and their British cousin initiated performances of short plays by Irish writers, with consequences affecting all their lives. Credible characterization, a lively plot and authentic background on Ireland as a country and a culture add up to a superior teen-aged story. Also, the exposition of parental attitudes toward the arts as a livelihood is valid. Wholesome entertainment with positive value.