This thesis, as its title implies, seeks to understand the life and work of Ngaio Marsh, particularly as this concerns her writing. Chapter One deals briefly with the relevant biographical material, much of which is new. Chapter Two constitutes a literary defence of the study of detective fiction with acknowledged artistic merit. Chapter Three involves an analysis of Marsh's craftsmanship, her qualities of style and characterization and a discussion of her principal series characters. Chapter Four touches on the distinctive features of Dame Ngaio's New Zealand stories and English rural settings, finding points in common for both. Chapter Five considers the general influence of Ngaio Marsh's theatrical experience upon her writing. In the Conclusion a general summation of Marsh's career is presented.