After surviving a catastrophic starship blow-out, Delia Kemp finds herself stranded on the inhospitable, ice-bound world of Valinda, populated by the Skelt, a race of hostile aliens who will stop at nothing to obtain Delia's scientific knowledge. Escaping from the Skelt - assisted by a friendly chimpanzee-like alien and a giant spider-crab - she travels south through a phantasmagorical landscape as the long winter comes to an end and the short, blistering summer approaches. Pursued by the Skelt, she and her companions make a death-defying dash across the planet's inimical equator to meet up with fellow survivors from the starship, and a final journey to the valley of Mahkanda - where salvation just might be awaiting.