Once you finish the Demonic Science quest, talk to Dr. West to start this one. Take a truck back to the tribal leader, Koritoia Ope. You must escort Ope back to Mowen's boat. He won't get in a car or fast travel. Take the boat and then continue to follow Ope. You will have a bunch of tough encounters along the way.
When you get to the raised bridge, go down a level and then sprint jump to the other side, there is a ladder to climb back up if you miss. You'll eventually get to a cutscene and then you'll have to follow Yerema. Don't stop to fight, once you make it to the cutscene all the enemies that were chasing you will disappear. After that help Mowen fight the enemies off him and then bring Yerema to the boat. Then escort Yerema back to Dr. West at the Laboratory. Talk to Dr. West to finish the quest and start the Hard Talk quest.
Note: During the fight in the village, I encountered a possibly game-breaking glitch. It would save that I used my ammo and damaged my weapons, but it would not save any damage I had done to the enemies. I could not load to an earlier save so I had to build up my rage meter by kicking (which uses no ammo) and kill the thug and the butcher with that and take out the rest of the walkers by kicking. I don't know if this is a common glitch but be aware of it and make sure you can kill all the enemies or go in with co-op players.
ID Card # 075 - When you're almost back to the Laboratory, you'll have to open a gate for Yerema and kill a few zombies on a bridge. The card is sitting on the bridge.