Wil McCarthy dares to combine two branches of scientific study--space-travel technology and biotechnology--to create a chilling and very believable future as Bloom pits humankind against an enemy of its own creation, grown rampantly out of control.

In the late twenty-first century, man-made, self-replicating organisms called mycora--smaller than the tiniest bacteria--mutated and swept across the globe in a chain reaction so swift and deadly there was no time to act. No time to do anything but flee an Earth destroyed by the very science created to nurture and sustain it. Soon the entire inner solar system was consumed, incorporated into the lethal psychedelic bloom of the Mycosystem.

Scant years later, the remnants of humanity cling to the asteroid belt and the inhospitable moons of Jupiter. As the society known as the Immunity ekes out a precarious existence, fighting off the invasion of deadly mycospores while working feverishly to build a starship that will carry them to safety, an ominous discovery alters everything. Mycora are incorporating gene sequences to elude Immunity defenses--perhaps even to thrive in the harsh environment of the outer system. The only way to be sure is to journey into the diseased heart of the Mycosystem, from which no one has ever returned.

The starship is readied and a crew is selected on the basis of expertise--and expendability. But when sabotage forces an early launch, suspicions arise among the crew. Someone--or something--doesn't want the mission to succeed. As the starship rockets toward Earth, under relentless attack from without and within, the questions and the terror multiply faster than a contagion. Who--or what--is the true enemy? When is change something to fight--or something to embrace? And how can humanity forge a future for itself in the face of an unstoppable foe seemingly destined to overwhelm the cosmos . . . ?