It’s East of the Water Treatment Plant and South of the Beantown Brewery. If you’re unable to view the video, here are the details: It should come as little surprise, then that there is an alien weapon in Fallout 4. It can be a little difficult to find (there’s only one in the game), so here’s a quick guide to locating the unique weapon: We’ve known this for awhile, even before Fallout 3’s downloadable content Mothership Zeta. Mankind is not alone in the Fallout universe.