Redstone Mansion

This is a quite big mansion I finished for about a half a year ago. The mansion is not the entire map. A railway leads you too several different cities and towns. The mansion is built by hand in creative mode, no world editors. Between every floors lies a block high floors which contains all properly working redstone, creating a full functioning house with changeable water pumps, lamps and other. But there is more. In the mansion, you will find different clues, ehich may lead to an answer. Can you solve the hidden secret of the last owner of the mansion?