Sixteen-year-old Valerie vanishes from home in the small hours clad only in her robe and slippers. Three days later, Sister Joan finds her body abandoned in the convent's little Moor Schoolhouse. The dead girl is dressed in wedding white. A garland of leaves encircles her head and a thin red line runs round her neck. Valerie has been strangled. Sister Joan's feelings are mixed when her prioress bids her to assist in the investigation of this eerie crime. But when another young Catholic girl is similarly murdered, she vows to do her utmost to help Detective Sergeant Mill find the murderer. The faster the better, for the killer is assuredly mad-and now seems fatally attracted to Sister Joan's own tranquil, unprotected Cornwall convent....