When something went wrong with the sun, Earth had eight minutes before it knew.

Watching the screens at the solar observatory, Lin Shu first noticed a curve that should not have existed. Every time a flare reached the ground, the radio array received a second signal exactly one minute later. It was so faint that everyone had dismissed it as an instrument echo. Today, the echo spoke.

“Don’t activate the mirror array.”

The compressed voice broke in and out, but it gave Lin Shu’s employee number, the observatory’s access code, and details of an accident that had not yet happened. He replayed the recording three times before he noticed a low pulse in the background, keeping perfect time with the atomic clock on the laboratory wall.

The mirror array was humanity’s largest network of orbital reflectors. At dawn tomorrow, it was scheduled to light up for the first time, sending sunlight to a base in Antarctica trapped in polar night. Two thousand people there needed its heat. Switching it off might take away their last chance.

Lin Shu sent the signal to his colleague Su Mi. Instead of asking who was speaking, she asked, “Where is the voice coming from?”

“It points toward the sun.”

“The sun doesn’t speak Chinese.”

She opened the raw array data and pointed to the second peak. It had not come from the sun. On the far side of Earth, it had bounced off a probe that had been out of service for seventeen years before reaching them.

Lin Shu pulled up the manifest from the probe’s last transmission. It listed a single crew member: Su Mi. She sat beside him, her face slowly draining of color.

The broadcast sounded again. This time, the future Su Mi spoke more clearly: “Don’t save me. Shut down the mirror array first.”