Each of the double sided mats will have a floorplan on it (3 X 4 rooms), showing which rooms can connect to others. Some exits will be hidden passageways, that only some characters will be aware of, and others will be locked doors, which can be unlocked with keys. Some exits cannot be used, meaning characters need to plan their journey round the house.
Because the mats are square, each floorplan can be used each way up, and double sided gives another two options. The three mats can also be interchanged between floors, so if the math is correct, that makes 384 different house layouts! And that's before the rooms are placed randomly on top, so no two games will be the same!
The player characters are coming along, with a lot of research into the Victorian era needed to make sure everything stays in context, what the main occupations were, what had / hadn't been invented in the 1800's etc.