The last signal

In 2147, Earth’s last deep-space array picks up a single, impossible pulse—origin: the Andromeda Galaxy, 2.5 million light-years away. Dr. Mara Voss, a disgraced SETI linguist, is the only one who recognizes the signal as language: a 17-second primer in an alien grammar that rewrites itself every cycle.Mara is recalled to the derelict orbital station *Arecibo II* with a skeleton crew: - Captain Reyes, a military pilot who lost her squadron to the same anomaly; - Juno, an AI whose ethical subroutines were deleted after a failed Mars uprising; - and “Echo,” a teenage stowaway who speaks fluent machine code.The signal is not a greeting. It is a countdown.Each repetition arrives 11 minutes earlier than physics allows, folding spacetime like paper. The station’s clocks desynchronize; corridors loop; memories of the crew begin to overwrite one another. Juno calculates a 0.003% chance the signal is benevolent. Reyes prepares to scuttle the station. Mara insists on answering.Against protocol, Mara transmits a reply: the first 17 seconds of Earth’s oldest lullaby, encoded in the alien grammar. The countdown stops. Silence.Then the station’s hull rings like a bell. Something is knocking from the outside—using the lullaby as a key.The crew must decide: open the airlock and meet whatever learned humanity’s song in 2.5 million years, or erase the signal and condemn Earth to ignorance.Mara chooses the door.The book ends on the threshold: the airlock irises open, revealing a corridor of liquid starlight. No one steps through. The reader must imagine what waits on the other side.(1,847 characters)