Solomon Epstein, a Martian engine engineer, spends his career on iterative modifications to fusion drive technology against the backdrop of rising Earth-Mars tensions over mineral rights and the UN's aborted invasion of Mars under the "breakaway province rule". Years into his marriage to Caitlin Esquibel he buys a small yacht for in-system testing, and the novella picks him up about a year later, fitting one more magnetic coil exhaust modification before another solo test burn. The drive works far beyond his expectations - sustained acceleration well above seven g and a fuel readout that implies hours of burn time - but the thrust pins him to the chair and he cannot reach the manual shutoff. He suffers a stroke that takes his left arm and drops his hand terminal beyond his reach. Dying, Solomon recognises the implications of what he has built - the inner planets and the Belt suddenly within easy reach of each other, the strategic calculus permanently altered - and lets the expanse fold itself around him as the yacht accelerates on toward deep space.