Douglas Clark's novels make a distinctive contribution to the genre of detective fiction because of his ingenious means and methods of murder. His work draws upon his extensive knowledge of natural bacterial, plant, and mineral poisons; manufactured chemical poisons; and lethal combinations of normally benign substances. Clark's expertise derives from his geological studies at university, his military training, and twenty-plus years of working in the pharmaceutical industry. Of his twenty-six police whodunits, only five include violent deaths by means of gunshots, strangulation, blows from a blunt instrument, a hit-and-run car crash, or electrical shock. Instead, villains commit crimes with botulinum bacteria, arsenical gas released from iron pyrites, sodium aurothiomalate (gold salts), and deuterium oxide (heavy water). The plant poisons employed are derived from castor oil beans, laburnum seeds, croton oil seeds, and lily of the valley leaves. Manufactured chemical poisons include barbiturates, paracetamol, diazepam, promethazine chloride, hexachlorophone, monoamine...