The Shield is Earth's only defence. Rendering the planet invisible from space, it keeps humanity safe from alien invasion. The Actives maintain the shield - no one is sure how - but without them, the Shield cannot function. When an Active called Tobe finds himself caught in a probability loop, the Shield is compromised. Soon, Tobe's malady spreads among the Active. Earth becomes vulnerable. Tobe's assistant, Metoo, is only interested in his wellbeing. Earth security's paramount concern is the preservation of the Shield. As Metoo strives to prevent Tobe's masters from undermining his fragile equilibrium, the global danger