When the tail of the comet Bhaktul flicks through the Earth's atmosphere, deadly particles are left in its wake. Suddenly, mankind is confronted with a virus that devastates the adult population. Only those under the age of eighteen seem to be immune. Desperate to save humanity, a renowned scientist proposes a bold plan: to create a ship that will carry a crew of 251 teenagers to a home in a distant solar system. Two years later, the Galahad and its crew - none over the age of sixteen - is launched.

Two years of training have prepared the crew for the challenges of space travel. But soon after departing Earth, they discover that a saboteur is hiding on the Galahad! Faced with escalating acts of vandalism and terrorized by threatening messages, sixteen-year-old Triana Martell and her council soon realize that the stowaway will do anything to ensure that the Galahad never reaches its destination. The teens must find a way to neutralize their enemy. For if their mission fails, it will mean the end of the human race.