So, we are on the final step where we have to find the switch and somehow use the time bomb to activate something. We found that if you go to the saloon and shoot the dartboard with a balistic knife, the piano in the salon starts playing on its own. Also NO ZOMBIES have been spawning at all, not even a crawler.
Thats not the good part
If you go into the mansion right after shooting the dartboard, you will see the ghost playing the piano herself on the piano coming back from the mansion.
You also have the option to tip her 10 points where she will give you a free perk. However the free perk is unconfirmed yet.
We are theorizing that if you tip her enough, you will make it that she cant spawn in the mansion anymore and you can activate the switch on the couch in the mansion.
If you want to see this in action watch the livestream here, http://www.youtube.com/watch?v=KDJGQ3Z15Ek
ALL CREDIT for this step goes to myself (G0dFeLLaZx) , DuncanJamesClark, Bathy1, and riko salvator