Effectivement, Fal.
"If kept alive, Desmond disappears from the game after you exit the Underground Lab upon completion of A Meeting of the Minds. If talked to beforehand, he will mention traveling north to pursue his next rival, another "player" in the "Great Game", a Post-War struggle between former geniuses and billionares."
http://fallout.wikia.com/wiki/Desmond_Lockheart