Who is Patrick from Lullaby: A Novel and what is their importance?

Patrick was Helen's infant son. He died twenty years before the opening of the novel from an unknown cause that Streator later learns was the culling song. Unknown to anyone, Helen had Patrick's body frozen, hoping that one day she could find a way to bring him back to life. Because of this, Helen is determined to find the grimoire in the hopes that it will contain a spell to bring the dead back to life.