The Great Ship, so vast that it contains within its depths a planet that lay undiscovered for generations, has cruised through the universe for untold billions of years. After a disastrous exploration of the planet, Marrow, the Ship's captains face an increasingly restive population aboard their mammoth vessel. And now, compounding the captains' troubles, the Ship is heading on an irreversible course straight for the Ink Well, a dark, opaque nebula. Washen and Pamir, the captains who saved Marrow from utter destruction, send Mere, whose uncanny ability to adapt to and understand other cultures makes her the only one for the job, to investigate the nebula before they plunge blindly in.