A prospector announces to a crowded pub that he has struck gold, and later that night is found dead at the bottom of his mine shaft after showing off the nugget in the pub.
When he examines the crime scene, Police Surgeon Dr Lucien Blake is overcome with anxiety in the claustrophobic mine - a result of distressing war memories. Even in this state, Dr Blake spots clues no one else sees.
Chief Superintendent Lawson and Dr Blake break the news to the dead man's landlady, Margaret Reid, although her reaction makes Blake immediately suspicious.
Back home, Jean is fitting Mattie for a red bridesmaid's dress for her best friend Eadie's wedding.
When Eadie's fiancé, Russ, gives her a ruby and diamond engagement ring, Mattie wonders where he got the money. Later that night Eadie, and Russ sweaty with fever and an injured hand, turn up at Dr Blake's practice for medical assistance.
Dr Blake doggedly follows other clues and hunches, and it turns out the prospector may have picked a very unlucky place to find his gold.