Irrepressible Biddy Leigh, under-cook at the foreboding Mawton Hall, only wants to marry her childhood sweetheart and set up her own tavern. But when her elderly master marries the young Lady Carinna, Biddy is unwittingly swept up in a world of scheming, secrets and lies. Forced to accompany her new mistress to Italy, Biddy takes with her an old household book of recipes, The Cook's Jewel, in which she records her observations. When she finds herself embroiled in a murderous conspiracy, Biddy realises that the secrets she holds could be the key to her survival - or her downfall.