The Code of Mr. Adriano's Death: (Detective Short Story)

If you were a detective and someone approached you and told you that he had just killed someone and was challenging you to prove that he was the murderer, what would you do? And if to annoy you even farther he would provide you with a clue to assist you in proving that he was the murderer. What would you do? Would you accept the challenge? Or would you turn away while thinking that such person was just perhaps “pulling your leg” or maybe was a mad person? This was what happened to detective...