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.

Pulaski assured Anya that the air filtering system would handle the threat of an outbreak. Adamant on her position, Anya insisted that she could not rely on the Federation's primitive technologies and that Hennesey was to be destroyed.

Anya proceed to morph into a large monster and approached Hennesey with the intention of killing him for Pulaski before she was stopped by Worf. (TNG: "The Dauphin")

Hennesey was portrayed by an unknown actor.