Irenon and the Cerenauts aboard her will be the final hope of thousands of colonists deserted after the failure of the AI deep space programme. The burden falls on Ingmar and Yuri, orphans both, chosen for their ability to cope with isolation and innate mental strength. But how to anticipate what level of strength might be needed when only one creature, the AI Danai, knows what waits for them out there in the darkness? Danger that cannot be seen, quantified, or understood. That will find them in their worst and best memories, the sanctuaries and horrors of their past and, eventually, the corridors of the Irenon herself. This is where Ingmar will finally understand the last words Danai said to her, a warning: Stay away from the lonely dark.