In a dying world, the Offset ceremony has been introduced to counteract and discourage procreation. It is a rule that is simultaneously accepted, celebrated and abhorred. But in this world, survival demands sacrifice so for every birth, there must be a death.

Professor Jac Boltanski is leading Project Salix, a ground-breaking new mission to save the world by replanting radioactive Greenland with genetically-modified willow trees. But things aren't working out and there are discrepancies in the data. Has someone intervened to sabotage her life's work?

In the meantime, her daughter Miri, an anti-natalist, has run away from home. Days before their Offset ceremony where one of her mothers must be sentenced to death, she is brought back against her will following a run-in with the law. Which parent will Miri pick to die: the one she loves, or the one she hates who is working to save the world?