Equinox, the longest day of the year, takes place within those twenty-four hours, starting at dawn on a September Saturday, 1923. George Mallory, the noted mountaineer is on his way to see his dear friend Duncan Grant. Duncan and Vanessa Bell (Virginia Woolf's sister) are alone, having sent off their children and friends, when they are both unexpectedly surprised by Mallory's visit. Mallory has come to persuade Duncan to accompany him on his last climb to Mount Everest. Vanessa does everything in her power to prevent this; however, during the course of the day into night - truths are revealed, passions are re-kindled and a roundelay of love, art and explorations between these three sometimes lovers begins and perhaps ends on the equinox.