The House of a Thousand Candles by Meredith Nicholson

A reputedly wealthy and eccentric old man dies in Vermont. His home, the House of a Thousand Candles, so called for the owner's preference to candle light, is left empty save a faithful servant -- his fortune mysteriously vanished, though rumored to still have been hidden in the house somewhere. John Glenarm, the late old man's grandson, stands to inherit the estate (and so the secret fortune) under the stipulation that he live in the house for one year. If he fails, the house will be forfeited and awarded to Marian Devereaux, the niece of the nun who operates the nearby Saint Agatha's School for girls. Mister Pickering, the executor of the estate and childhood rival of John's, decides to find the hidden treasure before young Glenarm does.