A member of Species 8472 disguised as a young human Starfleet ensign, captured by Chakotay and Tuvok in the simulated Starfleet Headquarters and brought aboard Voyager for questioning.
Ensign David Gentry appears in the Voyager episode In the Flesh. He seems to be an ordinary young officer in what looks like Starfleet Headquarters in San Francisco, but the setting is a simulation in the Delta Quadrant and Gentry is one of its inhabitants in human form.
When he grows suspicious of Chakotay, who is secretly recording the facility, Chakotay and Tuvok stun him and take him back to Voyager. In sickbay the Doctor finds that his human appearance is being maintained artificially.
Questioned by Janeway, Gentry chooses death over capture and releases a toxin into his own body. As he dies he reverts to his true form, revealing to the crew that the impostors are Species 8472.