What this plugin exactly does?
The main purpose of this plugin is to make an administrator invisible to the eyes of all other users.
The administrator that activate it will be hidden to any other user in every page of dashboard and frontend in your WordPress site.
The plugin will hide itself as well. Only the hidden administrator will see it and may eventually deactivate it.
This, of course, to avoid revealing the trick to everyone.
Although the plugin is hidden it is still operating. Similarly, the hidden Administrator retains all its functions: can login, administrate site, recover his own password (if forgotten) and so on.