Hennesey was a Human male who lived aboard the USS Enterprise-D during the mid-2360s. In 2365, Hennesey contracted Andronesian encephalitis when the ship's transporter filter was disrupted by a cosmic ray burst. Doctor Katherine Pulaski was in the middle of treating Hennesey when Worf and Anya entered sickbay while on a tour of the ship. When Anya saw Pulaski treating her patient, she inquired to what his illness was, only to acknowledge it as a contagious disease that may threaten Salia.