Mathematician Lakshmi Nayak receives a letter from her future self about faster-than-light travel. The equations work, and the letter itself seems to prove the possibility will someday be realized. But her paper on the topic is fiercely criticized, and she's warned away by a sinister Alliance agent. After defecting to the Union, she gets an unexpected offer: "I can build your ship." Shipbuilder John Grant learns of a secret project, which unknown to the world has been traveling to the stars for decades: Black Horizon.

The planet of Kiln is where the tyrannical Mandate keeps its prison colony, and for inmates, the journey there is always a one-way trip. One such prisoner is Professor Arton Daghdev, xeno-ecologist and political dissident. Soon after arrival, he discovers that Kiln has a secret. Humanity is not the first intelligent life to set foot there. In the midst of a ravenous, chaotic ecosystem are the ruins of a civilization, but who were the vanished builders and where did they go?

The Hygrometric Dehabitation Region, or the "Zone," is a growing band of rainforest on the equator, where the heat and humidity make it impossible for warm-blooded animals to survive. A human being without protection in the Zone is dead in minutes. Twenty years ago, Marks went into the rainforest with a group of researchers led by Doctor Elaine Fell, to study the extraordinary climate and see if it could be used in agriculture. The only thing she learned was that the Zone was no place for people. There were deaths, and the program was cut short. Now, they're sending her back in.

Drake, a retired police detective, receives a call in the dead of night from an alien-obsessed podcaster. He hastily departs for Montana the following morning. The phenomenon continues all over the globe. What are they? What do they mean? Britt is on assignment for a digital magazine when she encounters one of the Glass in a tragic boating accident, leaving her no choice but to follow the lead. Panic ensues as mysterious creatures are sighted.

The day that changed Melody's life was like any other over the previous two years. She'd found she had a gift for writing, and her career as an author had almost healed the pain of losing her job. When the Secret Service rang her bell, everything changed. Something was nearing Saturn…and it was slowing down. Had she been right about the object?