Mission 1; Missable. In a part of the map that is not shown. You’ll know you’re there when 73-Q says the area is heavily fortified & she can run out to distract. You’ll be at the top of a hill. If you run down it, look left, run that way, you’ll climb another hill leading to a nook. From the nook, you can look right to spot a bridge. There’s your box!