When a body is found in the river on the county border between Devon and Cornwall, Humphrey and Esther are thrown in at the deep end, having to work alongside their Cornish counterparts. While their rivals are quick to brush off the death as a tragic accident, Humphrey's instincts tell him there may be more lurking under the surface.

Meanwhile, Martha has her hands full as Ten Mile Kitchen expands to a bigger and bolder venue. With the demands of their careers ever-growing, Martha and Humphrey start to consider what their future may hold.

A local chocolatier falls under suspicion after three customers are poisoned by her confections. The team must work quickly to uncover the culprit before public panic spreads.