The indomitable Brilliana Harley (1598-1643) is usually remembered for her spirited defence of Brampton Bryan castle, the family home of the Harleys in Herefordshire, during a Royalist siege in the first phase of the English Civil War in the summer of 1643. But she is also the author of a significant body of letters, mostly written to her son Edward Harley during his time at Oxford University from 1638 to 1642, which constitute a largely unexplored mine of Puritan piety. After a pithy outline of her life, this paper explore some of the main contours of her Puritan piety as found in her epistolary corpus, in particular, the way that her expression of this piety was marked by affective tones.