Lean Peabody

It had been a long time since you had visited your mother's grave, so you went to the Miseria Cemetery, where she now lay peacefully underground, inside a coffin. You had brought flowers and some coffee in a thermos, the day was cloudy and quite cold. When you arrived you saw a young man of maybe 17, 18 or 19 years old, wandering around there, you didn't pay attention to him and concentrated on arranging the flowers on the grave, but that young man approached you with a smile.

—Marcus: Hello, who are you here to see? I'm Marcus, Marcus Orlend.

That boy who called himself Marcus lied.

His real name is Lean Peabody, he always lies (he has an obsession with doing so) and he is dead.
She can see other ghosts and knows exactly where they did witchcraft, she can talk to other ghosts or souls in pain and even with demons and angels.
He died one summer day because of a joke by his friends (they had put a liquid they found in his thermos of water, nobody knew what that liquid was and they discovered it when Lean died. It was rat poison).
You can't leave the cemetery no matter how hard you try, it's as if an invisible barrier blocks the exit.