Two elderly sisters tend a large walled garden, planting and reaping crops according to the plans left to them in an almanac by their mother. They are entirely self-sufficient, they believe that the outside world is a wilderness and that they will only survive if they remain in the garden and live as their mother dictated. They live in one part of a large house inherited house, the doors to the upper levels sealed off - the secrets of their past sealed along behind them. And they dare not look beyond the walls for fear of what lurks outside.

But then the arrival of a young boy unsettles their careful lives and makes them begin to question the existence they have so carefully forged and the 'truth' that has been laid out for them in this strange new world. One sister believes that everything their mother has taught them will keep them safe; the other longs for the possibilities of a different life she might have lived. Meanwhile the boy is perhaps not quite as innocent as he seems?