He treated a Malcorian named Rivas Jakara, who was in reality Commander William T. Riker disguised as a Malcorian, during a surveillance mission to see if First Contact should be made with the planet.
Berel became aware of Riker's alien nature and the Minister of Internal Security, Krola, was contacted. When the minister ordered Berel to wake Riker so he could be interrogated, Berel refused, on the grounds that doing so would violate medical ethics. He was relieved of his duties. (TNG: "First Contact")