The Man of Gold — H.R.F. Keating

For a respectable governess like Harriet Unwin, her first few weeks in the shabby, inhospitable home of the Partingtons were as unhappy as any she could remember. The bone-chilling cold, the grim sparseness of the meals, the embittered meanness of old Mr Partington: But for the kindness shown by his son, her spirit must surely have been crushed. But worse was to come for Harriet. Her chance discovery of the old man''s cherished secret was, she felt sure, the cause of the attack that finally stilled his heart.

The doctor, however, thought otherwise. It was neither illness nor old age that killed poor Mr Partington. It was poison....