Isabelle Duchamp's journal is a book in the Blood and Wine expansion for The Witcher 3: Wild Hunt. It can be found near the Termes Palace Ruins, at an abandoned campsite slightly east of the map marker.
Logbook of the archeological expedition under the guidance of Isabelle Duchamp.
Our excavation is underwritten by Oxenfurt Academy. Its goal is to study the ancient elven ruins at Termes and subsequently locate and find a way into the underground chambers beneath them using the Purple Ruby of Aed Gynvael.
We have pitched camp and conducted preliminary reconnaissance.
[illegible fragment] ....and the quarreling continues. The witcher advises us to end the expedition and someone has yet again brought up that canard about an ancient curse. [illegible fragment]
The entrance to the underground chambers is indeed protected by a barrier. We must await the witcher's return – he is to use the Purple Ruby to-- [illegible fragment]