Rianna and Bobby are Canaries—two of the living toxin monitors who are the Coalition for North American Survival's best tools for predicting and enduring an outbreak of the poisonous Clouds that threaten to destroy all life under the Dome.

Their heightened sensitivity to airborne toxins coupled with bioengineered tweaking, training, and medications means they can take data on current conditions as they affect living beings—and tolerate higher exposures than most people.

More than that, Rianna and Bobby are a couple. They're the two best forecasters of Cloud behavior, prized and protected by their supervisor, LeBrand, because of their complementary talents.

So why are their bosses trying to kill them?

What's the real agenda—and just how bad is that last Cloud formation going to be?

Can Rianna, Bobby, and LeBrand manage to stay alive long enough to find out what's going on?