Complete lockup in KMail

Hello lists,

Now I'm completely stuck. I have a duplicate pair of messages in my Gentoo-
User folder that cannot be retrieved from the database. There's no sign of 
them in the ~/.local/share/local-mail/.Linux.directory/Gentoo-User 
directory. I've tried to delete them in KMail. I've tried using 
akonadiconsole to identify them, and to move them to another folder - but it 
was only showing four messages from months ago. I don't know how to use 
akonadiconsole to fiddle with the database.

How can I get rid of this duplication? Until I do I can't make archive 
backups or even read e-mails.

This is kde-apps/kmail-16.12.0-r1.

-- 
Regards
Peter