Dr. Mulbray was one of Indiana Jones' colleagues at Barnett College. He and another colleague, Professor Stanton, approached Jones shortly after his return from the Portuguese Coast and asked him to authenticate a fertility idol. Jones proved it was a fake by breaking it in half and showing Mulbray and Stanton the cross-sections.
Neither Mulbray nor Stanton appear in Indiana Jones and the Last Crusade or its script, despite being listed in the credits. However, they are in the novelization but not identified by name.