The House of Doom

A group of 5th graders, along with their classmates, received letters in the middle of a warm fall. The letters were from someone unknown. The person it was signed by was believed to be dead. The students had been invited to a sleepover in an abandoned home.

The group was made up of: Leo Belle (10), Emily Belle (9, due to her exceptional skills in school she was moved up a grade), Iris Wolf (10), Amelia Taylor (10), Jake Mitchell (10), and Ivy Green (10). Ivy only joined because she followed Emily everywhere.

Can these six figure out who is behind this?