Set on a sailing boat as it travels from Tahiti to New Zealand, Debatable Land is a story of memory, childhood and longing. On board Ardent Spirit are the painter Alec Dundas, escaping a destructive, failed relationship; Logan Urquhart, the restless skipper; his troubled second wife Elspeth, who fears Logan is slipping away from her; Nick and Sandro, two marine nomads; and Gabriel, an attractive young woman who captivates the men.

As the ship sails from island to island, the inner dramas of these six disparate individuals spill over into their relationships with one another. But when a storm arrives, they are wrenched from the personal and forced to face the present danger.