The Department of Internal Operations was a PPC Department that went after Mary Sues that infiltrated HQ itself. That it even existed is not common knowledge — in theory, only the Flowers and members of the department itself knew about it — and all non-members were neuralysed on contact with it. It was headed by the Elm. According to Peter Piper, if the DIO's existence were to have become common knowledge it would have caused a public outcry against the Board of Department Heads, which was likely to end in a second Reorganisation and the deaths of the DIO's members. [1]