Life can evolve. Amena saw the evidence on an ancient Earth. It wasn't pleasant evidence, and it wasn't evolution into sentient life, but she saw evidence. So okay, she accepts that no little green men exist on alien worlds, but maybe one of these other Earths holds evolved humanity. Evolution faces a powerful obstacle, however - humanity itself. Volume 2: We Must Evolve begins with the discovery of a mysterious ark full of refugees caught in orbit over Pluto... Wait, an ark full of refugees...? Well, that's one Earth that's not evolving. But another could be doing better. It's possible, Amena keeps telling herself... Continuing the action-packed Earths in Space series, We Must Evolve features a novel-length journey told in four novellas - "The Pluto Factor," "Worlds to Save," "The New World," and "On Hold."