Laura's disability
Think I missed this part when the medium grabbed her arm, what was Laura's illness/disability and the reason why she was in that particular orphanage in the first place?
TIA
The medium grabbed her arm to make her listen to her and to show her the signs of her illness. She says that Simón was dying, as she is, and that was why he could see the ghosts.
Laura had no disability so she was the last one adopted from that orphanage.
"Begin at the beginning and go on till you come to the end; then stop."
The medium reached out and pinched Laura's arm which caused Laura to jump a little because it hurt. This was for illustration. That one pink pinch mark showed on Laura's arm, but this was nothing compared to the marks on the medium's arms indicating that she (the medium) is close to death and so she can see ghosts. At this point, Laura (correctly without a disability or illness) can't see ghosts.