You can get this quest by finding the corpse of an Imperial guard named Alethius . First, go to the Understone Keep in Markarth . While you're here you may as well kill two birds with one stone, so talk to the court wizard, Calcelmo , who is off to the left section of the place and ask him about the excavation.
He'll mention killing a spider named Nimhe , so agree to do it for a miscellaneous quest. Go into the nearby ruins ( Nchuand-Zel Excavation Site ) and kill the spider. In that same room is Alethius' corpse. Examine it to find a journal mentioning an expedition group. You'll now have this quest started and will have to " Recover Stromm's Journal ".
From the corpse, burn down the nearby cobwebs and proceed into Nchuand-Zel proper. Here you will be fighting the Falmer. Head out into the city and watch the floor for traps, then kill two falmer on the walkways. Follow the walkways killing falmer until you reach the 'Nchuand-Zel Quarters'. Enter them.
Here you will kill two more falmer before reaching a split where you can either go down or stay up. Head down, as this leads to Stromm's corpse. Of course it is guarded by 3-4 falmer, but take them all out and examine Stromm's corpse by the tree to read/get his journal. There's a bedroom nearby with a skeever and another falmer in it if you wish to take them out and loot.
You'll also see an imperial corpse and several falmer corpses as they made their stand here. There's nothing left in the Quarters for us now except looting and killing, which you can do if you wish (there's no real treasures of note). We'll be told to find the rest of the journals now, Staubs', Krag's, and Erj's.
Head back out to Nchuand-Zel (you can take the upper path in the quarters for another door back to the main room that leads to a chest) and from the walkways or the chest make your way to the lower levels and enter the door leading to the 'Nchuand-Zel Armory'.
In here you'll have to kill two falmer right off the bat. Take the lower path now to a locked door leading to the armory proper. Unlock it and you'll see Erj up by the main chest. Loot him to get his journal. Once you open up the big chest here, two Dwarven Spheres will attack from each side of the room, so be ready!
There's also a ton of side doors here to pick and loot (if you can handle the locks) for plenty of exra treasure, including a full set of Dwarven Armor. Take the only other path here and kill two falmer and a skeever to find a path back out to Nchuand-Zel.
You'll be back out on the walkways now, but on a different part. You'll see a small camp up ahead where you'll find Krag's body. Loot if for his journal then continue on to the door to enter 'Nchuand-Zel Control'. Head in and journey on. You'll kill two sets of two falmer before reaching Staub's body. Loot it to read his journal and learn of the automated defenses he was trying to turn on. Now it's our job!
Continue forward and you'll soon have to fight FOUR Dwarven Spiders. Not too hard, but most of them come from your flank, so watch out! Past that will be two Dwarven Spheres in a wide open area. There's just one more falmer to get through and then you'll be in the control room.
Flip the lever to turn on the defenses and then loot the chest here. The door behind you will be open to, and leads to another chest and a fast exit back to the main room.
Out here you'll see a falmer fighting a Dwarven Sphere. Hehe. Well, even though we are the ones who turned on the defenses, they are certainly NOT friendly to us! For example, to your right is a Dwarven Centurion that is just itching for a fight (kill him off for several goodies!).
We'll now be told to find someone who knows about the expedition. Make your way back to the Understone Keep now and talk to Calcelmo. You'll end up telling him what happened to the researchers and he'll end up giving you 1000 Gold in return for their notes. This will end this quest as well.