Deakin and Croft investigate a blackmail threat against a supermarket owner, after Stamp and Garfield are handed a contaminated pie which has given a woman food poisoning. Boulton attempts to use state-of-the-art forensics to decipher indentations on one of the ransom notes, while Lines speaks to an ex-employee who initially denies all involvement – until he discovers that the victim of the contaminated pie is none other than the woman's daughter.