I think this is one of the best Nancy Drew books. Nancy and friends attend a wild animal show where they meet Rishi and Rai. Rai treats the young Rishi horribly and Rishi runs away by hiding in the trunk of Nancy's car. When Nancy starts digging, she finds that Rishi is more than an abused boy - he's the son of a maharaji. He was kidnapped when he was very young and believed to be dead. Luckily, he meets Nancy and there is a happy ending.
I remember devouring these books in junior high, but this one was new and quite delightful. Looking forward to reading my next book in the series.