Below is a walkthrough on The Key to Humanity side quest in Dying Light 2 Stay Human. To obtain this quest, speak with the son of a scientist at the Smokehouse in northern Quarry End.
Search the dark hollow for the mysterious CD
Change the time to night then travel northeast to the objective. Once in the Dark Hollow, head down to the bottom floor and make your way into a bedroom. Kick open a boarded up doorway to enter a kitchen. Pick the hard lock on the door in the kitchen then loot the room to find the CD in a duffle bag on the table.
Bring the CD to the scientist
Travel to the Bazaar in Trinity and speak with Stellan to complete the quest.
Rewards
- 750 Combat XP
- 150 Old World Money