This is a story about these siblings Leonie and Lionel (one obsessed with mysteries and the other who is younger just had to follow her sister up) who find this green case with some riddles and clues and well, of course, they want to find out what it means.

It's a simple story really, typical for kids and tweens set in the summer break. Lionel is autistic, but I'd say he isn't really well written in that aspect, because it feels stereotypical in being male and extra smart. He doesn't really act like one… and honestly Leonie's mystery obsessions to the point when she couldn't sleep felt more autistic than her brother who was kinda distant sometimes… weird.

The mystery was fun, though I saw it coming, but still fun. It's set in Australia during a visit of the fictional princess of Saudi Arabia (there's a real princess of Saudi but, this one is fictional, not the real one), and well that ties into the story. I found the absent parents kinda annoying, because they weren't around much during SUMMER break, and let the kids with this very incompetent babysitter, yikes. But as kids' stories go, it went all well in the end. A quick and enjoyable read, I recommend to 10-12 year olds who like mysteries.