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

Waltraud Wagner is a nurse. He committed his first murder when a home-bound patient asked her to take her life in order to give her peace from her pain. Wagner later went to work in a hospital, where she specifically worked with the elderly. She began killing her patients in order to relieve their pain..... but she soon followed these mercy killings with killing the ones who annoyed her. Eventually, Wagner got several other nurses in on her scheme. These women would often talk about their kills in a local bar, and it was during one of these brag sessions that a local doctor overheard their conversation.