The skeleton in the closet / M.C. Beaton.

Enhanced descriptions from Syndetics:

Poor Fellworth Dolphin has been living under the thumb of his miserly, cold-hearted mother for far too long. Since the death of his father, Fellworth has been supporting both himself and his mother with the meager wages he earns as a waiter in the local hotel. When his mother suddenly dies, Fellworth is shocked to find that she has left him a sizable inheritance. Not knowing where the money could have possibly come from, Fell teams up with Maggie, a plain girl with a similar background, to figure out where the riches came from. Could Fell's late father have had a hand in a long-ago train robbery? What secrets surrounding the Dolphin family will the two sleuths uncover? As they poke around the village for answers, Maggie and Fell embark upon a surprise-filled path to danger and adventure, and-just possibly-love.With the same charm and wit that characterize her Agatha Raisin series, "the always wonderful M.C. Beaton" (Romantic Times magazine) has created yet another charming mystery in the best of the cozy tradition.