Deep within the bowels of the USS Darkstar.
Hey buddy, don't tap on the glass.
 Is it a screenshot or a photograph?
A crew member enjoys the alien view.
"Black Widow Inc. would like to invite you to join our organization. You [will] be assigned as a member of the multi disciplinary scientific team on board of the USS DARKSTAR, in a zoological research expedition to seek out, collect and investigate new alien life-forms in unexplored sectors of the universe." ~ from included readme file.
Arguably the most successful and imaginative independent level author for Quake I and II shines his creative light on Half-Life, threatening in one release to render all previous level additions for Half-Life inconsequential, while at the same time raising the bar chin high for all future levels to follow. USS Darkstar is a mighty level debut which quickly puts aside any doubt as to whether or not Half-Life level authors can compete with Quake. They can. Level for level, frag for frag, USS Darkstar is the Half-Life equivalent of any of the best Quake single player experiences to date. 
Those familiar with Neil Manke's work for Quake will recognize his handiwork here as well. Neil's penchant for humor and the unexpected are right at home among Half-Life's scripted events. What starts as a pleasant excursion in space aboard a zoological research vessel quickly turns into a nightmare of alien proportions. With the containment force fields damaged the alien specimens quickly escape and begin their rampage of terror. Your mission is twofold, find a means off this doomed ship and avoid becoming some aliens afternoon trapped gas. In other words...stay alive!
Gameplay is excellent with plenty of combat, puzzles and suprises. The sheer length of the level pak itself (16 player levels) is astounding. If this had come in a shrink wrapped box at your local software store you would not have been disappointed. As such it is important to pay attention to your health and suit (armor) status. For a stretch I found myself limping along with only one health! Neil and company round out the gameplay with professional voice acting, changes in gravity, a very big change in perception (heh heh), interactive trams, and excellent architecture (Neil's space ship construction prowess is without equal, evident even back in his Quake I Starship days.) The opening and closing video help to make this a complete production.
TITLE:                   USS Darkstar
AUTHOR:             Neil Manke
Design/Technical Advisor:            Einar Saukas
Lead Tester:     Paul Taylor
Sound Producer:   Magnus Jansén
DATE:                  May 20, 1999
FILESIZE:        11.15 MB
DOWNLOAD:        PC Gamer. Look for the link for USS Darkstar in the FEATURES section.
H I G H S:
Great story line, wonderful theme executed perfectly. Excellent build with all the game play extras.
L O W S:
Addiction factor high, write a note to the wife and kids.
N U T   S H E L L:
Finally, a level pak that proves once and for all that Half-Life editing can compete with Quake in the single player arena.

Darkstar Trivia

See if you can spot this Quake Map Hotel produced insignia in USS DARKSTAR!