Updating the topic now that we have this listed as an affiliate game. I'll splat it on the links page at some point.
For a quick summary, you end up in a nice house with a cast of characters and there is a mystery afoot - the "stolen diamond ring" of the title. You poke around and visit various locations meeting all the characters and try to work out what really happened. The game has some cute features that will automatically take notes for you and draw relationships between the characters to help you figure it out.
It's not all that long, and there's only one solution to the mystery. However, it's cheap, and the characters are cute. So
check out the demo and see what you think.