Pyre is a volatile planet. Its surface belches heat and noxious gases, forcing downsiders to inhabit domes. But Pyre's instability isn't limited to its geology. The colonists, who were marooned in the system hundreds of years ago, have endured a tumultuous history.
Exploring Triton, Pyre's third moon, spacers inadvertently activate an alien dome. When nothing came of it, they combined their mining ships with the Honora Belle, the aging colony vessel, to sling slush, frozen gases, at Emperion, Pyre's second moon.
Nearly a year later, the Belle's bridge crew, who monitors the alien site, is alarmed, when they witness a bright blue light shoot from the dome's platform and merge with the shield. The alien site isn't an entertainment stage, as Captain Jessie Cinders had facetiously mused. It's a gate, and aliens have arrived.