There are exactly three victims in this game!
I think that's a little narrow minded. The character will no doubt be scarred for life by this tragic event. I'm sure the entire family will be affected by sadness. Even the owner of the mansion is bound to be a little scared that's there's a murderer on his property.
Back on topic though, I've been thinking about how you could threaten a cousin to do as you please or use some kind of drug but it all leads back to the same problem:
How can you leave a perfectly sealed room without breaking one of the seals?
Unless the doors had cat flaps... But then it wouldn't be perfectly sealed.
Am I at least on the right path or just chasing red herrings?
1 more thing:
Other than the door and the window, there exists no way that a human could enter or exit a room.Does this mean at the start of the game or throughout the game entirely? I mean, could the culprit create another way out the room? If so then
The culprit approaches the house. The windows are open because the weather is hot. The culprit enters each room, sends the cousin on a visit to st peter and then leaves swiftly through a window (leaving it unlocked). After all 3 cousins are dead, the culprit enters a room, open the common room door and uses knock-out gas, chloroform or something like that to stop you from waking. The culprit returns to the guestroom, locks both the door and the window. The culprit moves the chest of drawers and, using a saw, creates a hole just big enough to crawl through on the wall behind the drawers and leaves. The culprit used a sucker/ plunger or created some kind of handle to move the chest of drawers back into place in front of the hole. On the outside, the entrance could be covered by placing the removed material in the space and sticking a potted plant in front. Do this for all 3 rooms.