Brymn was an archaeologist, and much of his research had focused on a region of space known as the Chasm, a part of the universe that was literally dead, all of its worlds empty of any life-forms, though traces existed of the civilizations that must once have flourished in the region. Brymn had sought out Mac because she was a biologist -- a discipline strictly forbidden among his own people -- and he felt that through her expertise she might be able to help him discover what had created the Chasm. But Mac had little interest in alien races and in studies that ranged beyond Earth, and as politely as she was capable of, she tried to make it clear that she was unwilling to abandon her own work.

However, the decision was soon taken out of her hands when a mysterious and devastating attack on the Base resulted in the abduction of Emily, and forced Mac to flee for her life with Brymn and the Earth special agents who were escorting him. Suddenly, it appeared that Earth itself might be under attack by the legendary race the Ohryn called the Ro, the beings they thought might be the destructive force behind the Chasm. Cut off from everything and everyone she knew, Mac found herself in grave danger and charged with the responsibility of learning everything she could that might possibly aid Earth in protecting the human race from extinction...