The Valakian doctor who leads the effort against the genetic disease killing his people.
Esaak is the director of a Valakian medical clinic. In Dear Doctor he welcomes the Enterprise crew after his people ask for help with a disease that threatens more than fifty million lives, and he shows Phlox, Archer, T'Pol and Sato around his facility.
Phlox comes to believe that the illness is genetic and that the Valakians are dying out while the Menk, who live alongside them, are beginning to awaken. Archer decides not to provide a cure or warp drive, giving the Valakians medicine that eases the symptoms instead, leaving Esaak's people with an uncertain future.