It is 1897 and three years have passed since Rose McQuinn's husband, Danny, disappeared in Arizona. Believing him to be dead, she returned to Scotland to start her life afresh. She has now fulfilled her ambition of becoming a 'Lady Investigator, Discretion Guaranteed' and is about to marry her lover, Detective Inspector Jack Macmerry of the Edinburgh Police. But pre-wedding jitters become the least of her worries when a nun from the local convent claims to have received a letter from Danny. Is the elderly nun simply confused, or could Danny really still be alive? Unnerved and determined to find out the truth before her wedding, Rose begins to investigate. However, after two suspicious deaths, all the signs suggest that a ghost is about to walk back into her life.