Seeking the name of a mystery novel, urgent

The article unfolded from two perspectives. The beginning seemed to be about the kidnapped person in a cave in the forest. He kept saying something like "Mom, save me" and even placed the branches into an SOS. The other perspective was the main character. There was also a description of the dog transporting the corpse. It had been a long time since the kidnapped person was finally found. The kidnapped person had died a long time ago. It seemed to be a trick to use time. I don't know how to describe it, I hope someone has seen it

Answer 1

An example of a mystery novel's name was as follows:

Lock of the Secret Chamber

The story was about a rich businessman who was murdered and the police needed to find the murderer through a seemingly ordinary secret room. The protagonist and a policewoman enter the secret room together and gradually reveal the truth by unlocking various locks and puzzles. This story was full of elements of reasoning, but there were also many suspense and twists that were fascinating.