Lena - a deep-ocean biologist, analytical, counting to keep from being afraid - and Harlan - a pilot who has already been here once and did not come back the same - descend 4,000 meters in a submersible that smells like the last person who sat in it. To Bathyal-7, a research station abandoned two years ago on a shelf of what the report calls "calciumite substrate of indeterminate biological origin" and what Lena, looking down through clean water that should not be clean, can only call bone. A reef of bone the size of a continent. Ribs fused to jaws. Skulls the size of cars. Pulsing.