Love this! Better than Myst, I'd say. Reminds me a lot of The Room series.

There's no hand holding: you're just exploring a big mansion with lots of secrets, nooks, and crannies. So hard to come by these days... Click EVERYWHERE. I didn't pay that much attention to the story, but the puzzles and the exploration are very well-made. I also love the fact that it's point and click: no nausea, and runs on any old PC.