DCI Barnaby and DS Nelson investigate the murder of Eric Calder who was apparently poisoned by the biscuit tin of his own company while on a business trip to Copenhagen. Calder's family have been making biscuits in Badger's Drift for over a century and the Danish police seek Barnaby's help in investigating matters at his end. Calder had a wife Penelope, a son named Harry, and a younger brother Julian. The dead man seems to have had few friends and was in Copenhagen to supply product to a Danish firm. His right-hand man in the business was his master baker, Armand Stone. Barnaby quickly determines that the contaminated package Calder received at his hotel originated in his own company's mail room. Dr. Wilding confirms that Calder died from strychnine poisoning. This points the finger at Stone, who has a background in chemistry, but he says Calder and his son Harry had a huge row recently. In Stockholm, they learn that Calder was planning to reunite with a woman he had left long ago but the solutions to the deaths are found at the biscuit factory and the recipe for their best-selling product. In the midst of the investigation, Sarah goes into labor.
—garykmcd