The secrets that we keep. That's the subject of All The Beggars Riding, Belfast-born writer Lucy Caldwell's third novel.
It's this year's choice for the One City, One Book initiative, designed to get audiences reading and discussing the work of a contemporary local author.
Caldwell was present for the launch event of this year's programme. She was joined by Peter Sheridan, whose one-man stage show 47 Roses was a key source of inspiration for All The Beggars Riding.
At the heart of 47 Roses is a father who for four decades pursued a double life, divided between his wife Anna, and Doris, who lived in England.
Sheridan, an absorbing raconteur, recalls the shock arrival of Doris at the Sheridan home in Dublin, in the aftermath of his father's death. She bears 47 roses, one for each year of her liaison with 'Da', to place upon his grave at Glasnevin.
Sheridan eventually visits Doris in Blackburn, to probe the duplicity which enabled his father to flagrantly conduct a twin existence. What he discovers is the extraordinary, poignant story of a woman who waited 40 years to start a new life with her distant lover from Dublin.
It never happened, and Sheridan never knew his father's feelings on the subject.
Some secrets, it seems, are too deep to fathom, some people essentially unknowable, defying all attempts to cast light upon the inner darkness.