In Victorian Newcastle, secrets hidden for 18 years resurface when a stolen diamond with a distinctive reddish hue and a meeting between a young man and woman leads to forbidden love and a love triangle.

Belle is married to Marcel and begins to see signs he may not be the man she thought he was. Freddie has his own suspicions, and receives a hint that the key to the secret may be hidden in Harrogate.

Freddie and Belle learn the truth about Marcel in their own ways, which leads to a trap for each as Marcel tries to keep his secret.