To add some clarity to the above 'solution', as I was having issues locating Thebes; this is in the Boeotia region.
In the east of Boeotia there's a location called the Cursed Land of Oedipous
. If you don't see a quest show up on your map (the yellow !) then fast travel to the 'Kademeia' synchronisation point and walk north-east up through the town. The quest marker should pop up while there, just after passing the Arkropolis of Thebes.
From here you should hopefully have the quest The Hunting Party
which is the beginning of Hippokrates' questline.
After this you have to complete:Let My Patients Go
Fast travel back to Kademeia' synchronisation point, and look to the bottom of the Cursed Land of Oepipous location. Just south of the Sync point you're at. The new quest icon will show there.
You'll then need to complete:Inheritance Insurance.
Too Much of a Good Thing.
After which you should have your new achievement.