As Morse sees in the new year at an opera house in Venice, a murder in Oxford puts Thursday on a quest to find the man responsible. Returning home, Morse makes a new acquaintance, and old friendships show signs of strain.

Morse and Thursday team up to solve a poison pen case on Endeavour, but as the investigation of Fancy's murder comes to a head, they find themselves on opposite sides.

The death of a schoolgirl brings Endeavour back to Oxford. When he refuses to accept that the main suspect is guilty, Endeavour has to uncover the truth and rescue a victim before it is too late.