What’s the harm in trying to contact a loved one that has passed away?

The dead are in God’s hands. Jesus alone has returned from the dead, and He has told us all that we need to know about the mystery of the after-life. In the Old Testament it is explicitly forbidden to ‘call up the dead’, to try to contact the dead through mediums or other occult practices. Spiritualism and necromancy are not just open to charlatans and those who manipulate vulnerable people who are grieving and distressed, but can also lay people open to demonic forces which can do nothing but harm. This is why the Church views participation in such acts as gravely sinful.