There are many special achievements in The Lake House, and "Close Inspection" is one of them. To unlock this achievement, you need to go to the Laundry level and interact with the keyhole in the restroom. However, looking through the keyhole will reveal something unusual.
How to Unlock the Close Inspection Achievement in Rusty Lake: The Lake House
Close Inspection
Close Inspection
In the [Laundry] level, interact with the keyhole in the restroom.
Related Guide: How to Unlock the Perfect Hunt Achievement in The Lake House