Beatrice Morgan returns to her childhood home in inner-city Bristol, hurt and alone. Fired from her signals intelligence job, she mourns the Windrush-generation grandfather who raised her, certain she's failed him.

Loath to return to that secretive world, she keeps her coding and linguistic skills sharp running pattern analysis on SETI data. What she finds shouldn't exist: structured transmissions from an interstellar object hurtling towards Earth.

Working closely with an old classmate-turned-DJ to solve the riddle, their partnership ignites something she didn’t expect. Teaming up with her astrophysicist college roommate and an ex-punk xenobiologist, they race to decode the message before impact. As they pull on the threads, they learn of a looted Sumerian monument bearing an ancient prophecy both impossible and frighteningly accurate.

Amid growing civic unrest and with a secretive organisation hunting them, they realise that even if the object misses, everything is about to change.