1978. On holiday with their children in Oban, Nick and Rosemary Storey stumble across a stone hut filled with barrels of what seems to be illicit whisky. While on their way to walking nearby hills, they smell the unmistakeable smell of barley being fermented in a mash tun before distillation. But having overheard a conversation about the illegal whisky operation, Nick is unable to contact the local police or Excise officer. A chance remark and the arrival of the Customs cutter "Venturous" leads to a cat and mouse chase around Mull and the neighbouring islands. But there may be a price to pay for catching the whisky smugglers. "Copper Kettle" is the thirteenth book in a series of detective stores set in HM Customs & Excise, by Richard Hernaman Allen, a former Commissioner.