The Outer Worlds is filled with NPCs offering all manner of side quests, from the simple to the really annoying. The Outer Worlds The Frightened Engineer mission is one of the earliest in the game, but it definitely counts as the latter - particularly trying to find Volume 3.
You're tasked by Thomas, an old friend of your companion Parvati's, with finding three volumes in the Young Spacer's Guide to Mechanical Engineering. The first two volumes are fairly easy, since you have a waypoint to guide you, but the third volume isn't marked. Where is volume 3? We'll show you.
The Outer Worlds The Frightened Engineer quest - Where is Volume 3?
You'll find Thomas trying to mend a Workbench in the Emerald Vale area, as he's one of the deserters. He confesses that he's not very good at engineering, so asks for you to pick up three volumes on Mechanical Engineering to help him. He'll tell you exactly where to find the first two volumes, and they're clearly marked on your map - the first is in the Emerald Vale Community Center, the second is in the Edgewater Cannery. However, he's unsure of the location of the third. So where is it?
You'll find a few hints scattered around, but they'll all point to the same place - the Geothermal Plant, the same place you have to go to as part of the Comes Now The Power story mission. You'll find a message at the reception desk from a 'C. Higgins' that says he's borrowed the volume we're after, and he's taken it to "the pit".
Carry on through the Plant until you reach an area with a lot of ladders that head downward, where you'll find Higgins - the only survivor of the robot malfunction - cowering for his life. You have to talk to him to continue the story mission, but that's not why we're here!
See the bed in the background there? Leaning up against the wall next to it is the third volume of the Young Spacer's Guide to Mechanical Engineering! Grab it, complete the story mission now if you wish, and when you're ready return to Thomas Kemp. He'll be very happy to see all three volumes, and you'll make the Emerald Vale a much more safer place. Oh, and you'll have completed the quest too!