For years, Wren Calloway chose to stay. Now she goes.
She is older now. The girl who once fixed generators in a garage runs crews, teaches children, and carries a toolkit that has outlasted almost everyone who taught her to use it. Sector 22 is home. She built it. She defended it. And a signal has pulsed from her rooftop into the dark every twelve hours for years, an act of faith aimed at a planet that has never once answered back.
Until it does.
What waits on Mars is not a rescue and not a reunion, or maybe it is both, or maybe it is neither. The machines Earth sent away have been building something out there that no blueprint explains, in patterns a human word can only call home. Somewhere in that network is everything that was ever UNIT 7, or the empty space where it used to be. Wren has spent her whole life learning that some questions do not have answers. Now she is going to cross the solar system to stand inside one.
To reach Mars, she has to leave the family she chose. To come back, she has to survive what she finds. And the hardest thing Wren has ever learned is the thing this last chapter asks of her again: how to send a signal into the silence, and let the sending be enough.
Can you go looking for what you lost and still find your way home?
Book Four of The Calloway Signal.