Here's a breakdown:
* Plain: Simple, clear, and easy to understand.
* Sight: The ability to see.
Therefore, something "in plain sight" is right there, out in the open, and not hidden in any way.
Here are some examples:
* "The evidence was in plain sight, but the police overlooked it." This means the evidence was clearly visible, but the police didn't see it.
* "The thief walked past the security camera in plain sight." This means the thief was clearly visible on the camera, not trying to hide.
In short, "in plain sight" emphasizes the obviousness and visibility of something.