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 when three customers are poisoned after sampling her confections. Humphrey must explore every avenue to determine whether she orchestrated the attack or was framed.

The mystery deepens as the team finds no trace of poison in the remaining chocolates – how did the perpetrator ensure the victims ate the right one? With public panic spreading across Shipton Abbott, the team must work swiftly to uncover the culprit.