Herbert Powyss lives on a small estate in the Welsh Marches, with enough time and income to pursue a gentleman's fashionable cultivation of exotic plants and trees. But he longs to make his mark in the field of science. He hits on a radical experiment in isolation: for seven years a subject will inhabit three rooms in the cellar of the manor house, fitted out with books, paintings and even a chamber organ. Meals will arrive thrice daily via a dumbwaiter. The solitude will be totally unrelieved by any social contact; the subject will keep a diary of his daily thoughts and actions. Only one man is desperate enough to apply for the job: John Warlow, a semi-literate labourer with a wife and six children to provide for. The experiment, a classic Enlightenment exercise gone more than a little mad, will have unforeseen consequences for all included.