
If you have Lohse in your party, Malady will wait in front of his house and teleport you into Adramahlikh's realm where you have to make some moral decisions. Before you go to his house prepare yourself for this because this probably the hardest fight you will encounter (if you don't cheese). He will send you an invitation to his home (The Black House) if you either have killed Isbeil (The Secrets of the Dwarves) or Lord Kemm (The Vault of Linder Kemm).
A Royal Protector will talk to you after that fight and give you more information about the Doctor. It's full of exploding toys that you will have to deal with.
In Arx, Investigate the wedding cake you will find during The Secrets of the Dwarves quest. The tree spirit on Bloodmon island tells you the name of the doctor and if you speak with Jahan, he will tell you the doctor is currently hiding in Arx. You can acquire this quest from the tree on Bloodmoon Island.
Doctor's Orders is a side-quest in Divinity: Original Sin 2.