The Garden of Burning Sand by Corban Addison

Zoe Fleming, an accomplished young human rights attorney, has made a life for herself in Zambia, far from her estranged father - an American business mogul with presidential aspirations - and from the devastating betrayals of her past.
When a young girl with Down syndrome is sexually assaulted in a Lusaka slum, Zoe joins Zambian police officer Joseph Kabuta in investigating the rape. Piecing together clues from the victim's past, they discover an unsettling connection between the girl - Kuyeya - and a powerful Zambian family who will stop at nothing to bury the truth.
As they are drawn deeper into the complex web of characters behind this appalling crime, Zoe and Joseph forge a bond of trust and friendship that slowly transforms into love. Opposed on all sides, they find themselves caught in a dangerous clash between the forces of justice and power. To successfully prosecute Kuyeya's attacker and build a future with Joseph, Zoe must risk her life and her heart - and confront the dark past she thought she had left behind.