For thirty years, Dr. Harvey Griswold has been right about something no one would believe. The barrier between our world and an adjacent one is real, measurable, and under the right conditions, permeable. He has the evidence. He has the equipment. What he has never had, until now, is proof.

When a single late-night experiment produces four seconds of footage that changes everything, Griswold brings in Carl Betzlow — younger, sharper, and considerably less romantic about what the footage might mean. Together they begin pushing toward something that neither of them fully understands yet, and that neither of them will be able to walk away from once they do.

On the other side of the barrier, they are not working alone. A senior analyst named Xul has been watching the same phenomenon from the opposite direction for nineteen years, building models that his world's government does not want to hear and racing against a political faction that has decided the barrier's failure is not a catastrophe to be prevented but an opportunity to be exploited.

Two worlds. Two teams working in isolation toward the same terrifying conclusion. And a timeline that is running out for both of them.

What it costs to be right. What it means to reach across the impossible. What happens when the thing you spend your life looking for finally looks back.