A once-in-a-generation series, Ali Smith's Seasonal Quartet is a tour-de-force about love, time, art, politics, and how we live now.

In the present, Sacha knows the world's in trouble. Her brother Robert just is trouble.

Their mother and father are having trouble. Meanwhile the world's in meltdown - and the real meltdown hasn't even started yet. In the past, a lovely summer.

A different brother and sister know they're living on borrowed time. This is a story about people on the brink of change. They're family, but they think they're strangers.

So: where does family begin? And what do people who think they've got nothing in common have in common? Summer.