"The police tried to find out everything about my sister's death, because no-one trusted doctor Roylott. But they couldn't find out what killed her.

I told them that my sister's room was locked on the inside. The windows were closed and my sister locked them at night. The police looked at all the walls carefully but they could not find any doors or holes for the killer to come in by. They checked the floor too, but there was nothing there to help them.

The chimney is wide, but no-one can come down it. So I am sure that my sister was completely alone when she died. Also, it did not look as if anyone tried to hurt her.

"How about poison?" asked Holmes

"The doctors thought about that, but they could not find any".