The Lion Cub's Secret by Lauren St. John

After Martine saves an orphaned lion cub from a market, she dreams of keeping it at Sawubona forever. Then she learns that Tau, the cub, already has a home. He's been stolen from one of South Africa's most famous game reserves. When Martine and her best friend Ben are invited to volunteer at Marula Wilderness Lodge to help settle Tau in, they leap at the chance. But behind Marula's glamorous façade, all is not what it seems. Once Ben and Martine start asking questions, they're drawn deeper and deeper into the deadliest adventure of their lives.