The Bogeyman Caper by Susan Pearson, 1990.
This is part of the Eagle-Eye Ernie mystery series.
Everyone says that the old yellow house in their town, White Bear Lake, Minnesota, is inhabited by a bogeyman, but Ernie doesn’t believe it. She decides to prove to her friends that there is no bogeyman in the old house, so she finds ways to keep an eye on the house.
At first, all they see is a creepy-looking old cat. Then, William finds a strange bone in the yard, and Ernie sees a red glow inside and hears tapping sounds. Are her friends right about the bogeyman, or is there another explanation?
Ernie uses her powers of observation to determine that many of the spooky things about the house and its new owner are actually familiar, both to herself and her friends.