How to complete The First Biomarker in Dying Light 2 Stay Human

When you activate the Alder Windmill in the Trinity District, a Trading Post will be unlocked southwest of the windmill, close to the border between the Trinity and Houndfield districts. There you can meet McGregor, who’ll give you the The First Biomaker quest, along with a note from Dr. Katsumi containing a riddle with clues to the safe code:

• What becomes smaller when you turn it upside down?
• An odd number – take away a letter and it becomes even
• A little girl goes to the store and buys one dozen eggs. As she is going home, all but three eggs break. How many eggs are left unbroken?

After speaking to McGregor, go down to the street and around to the northwest side of the Saint Joseph’s Hospital. Climb the damaged strip of wall near the two ambulances, then jump over to the ladder and use that to reach the roof. Go to the left and climb up through the large square hole in the wall. The safe is in this room.

• A 9 becomes a 6 when you turn it upside down, so the first number of the safe code is 9
• If you take the letter ‘s’ away from the word ‘seven’, you get the word ‘even’, so the second number of the safe code is 7
• If all but three eggs break, then three eggs are left unbroken, so the third number of the safe code is 3

The First biomarker safe code is therefore 973, so enter 9 – 7 – 3 on its dial, and open it to get the first biomarker. Take it back to McGregor and he will give you an Inhibitor and the Confidential Notice to GRE Personnel.