Gradually, Betty learns her lover's terrifying family history, and Ashling's secret obsession. Knock Knock, Open Wide weaves horror and Celtic myth into a terrifying, heartbreaking supernatural tale of fractured family bonds, the secrets we carry, and the veiled forces that guide Irish life.

So begins a night of unspeakable horror that will take her to the very brink of sanity. She will never speak of it again. Two decades later, Betty Fitzpatrick, newly arrived at college in Dublin, has already fallen in love with the drama society, and the beautiful but troubled Ashling Mallen.