Look in the toolbox to find a screwdriver. Take the journal page from the small table and the magnet from the bench. Also take the phial of oil from the shelf above, and the bone saw from the bottom left of the screen. Try to go through the door to the left, but it is stuck. Use the phial of oil on the door, then the screwdriver to undo the hinges, then go through.
Pick up another journal page, then go upstairs and take the long stick. Go up further and take another journal page, then continue up to find a locked door - you will automatically look through. Combine your long stick and magnet, then use this on the exit to get the basement key. Use this on the door and head through.
Grab the next journal page, and also pick up the 3 cogwheels from the floor. Put these on their corresponding places on the wall, then turn the valve and go through the door.
Take 2 journal pages from the dinner room. Examine the mortar and pestle and the candlestick. Pick up the china bowl before heading left into the hall. Examine the body - pull on the strings and take the small key. Also take the candlestick and the journal page from the body. Grab a second journal page from the base of the stairs. Go through the door between the staircases leading to the outside world.
Pick up the frozen bottle of milk and the journal page, then head right and take another journal page. Examine the grave, then continue right to the greenhouse. Pick up the journal page and the lantern from the ground. Next take the belladonna plant from the left, and the journal page from behind it. Leave the greenhouse and return left into the house.
Go through the far left door into the living room. Pick up the journal page, then return right to the hall, and through the near left door into the study. Pick up another journal page from the desk here, then go left until you are stopped by a black cat. Return right twice into the dinner room. Use your frozen milk on the fireplace to thaw it out; pick it up again and pour it into your bowl. Next use your belladonna plant on the mortar and pestle, then use the powder in the bowl of milk to poison it. Return left twice and use your poisoned milk on the cat. Now pick up the mysterious item (which turns out to be another key) and another journal page. Use your tassel key on the door here and go through. Take the journal page here, then continue left once more.
Open the cupboard beneath the broken mirror. Take the rope from inside, then use your tiny key to unlock the locker. Take the big key from inside. Walk left and grab another journal page, then use the big key in Belladonna's back. Talk to her about everything (you need to learn the location of the mausoleum in particular), then leave her room.
Head back right twice to reach the hall. Go up and examine the grandfather clock, then use your screwdriver on it to get the clockwork mechanism from inside. Go right through the dinner room to the basement.
Head all the way down the stairs to the basement and examine the suit of armor. Combine your rope and lantern, then lower this into the dark entrance before climbing down.
Pick up the final journal page. Examine the sarcophagus, then use the candlestick to break it open. Use your bone saw to remove the head, then exit the mausoleum and go right to the laboratory.
Take the brain from the jar on the top shelf, then head right to where Belladonna is waiting. Give her the brain, head and clockwork. Now pull the switch on the wall.