Level of Difficulty: Hard

D.O was found dead in his bedroom by her maid, Tiffany.

Tiffany tell the Detecive, Kris, exactly what she's witnessed: "Just after completing my work, I noticed his study light was on and I decided to look in from the outside to see if he was in there. There was frost all over the window, so I had to wipe it away to see inside.

That is when I saw his body.

So I kicked in the front door to confirm my suspicions. I called the police immediately afterward."

How did Kris, the detective, immediately knows that killer was the maid.

Solved by ihartkyuhyun, 3rd time in a ROW!

Answer: Frost forms on the inside of the window, not the outside. So the maid could not have wiped it off to discover the body.