The Skeleton in the Closet — M.C. Beaton

IGNORANCE IS BLISS...
Ever since the death of his father, poor Fellworth Dolphin has slaved away as a waiter to support his miserly, cold-hearted mother. When his mother suddenly dies, Fellworth is shocked to discover that she has left him a sizable inheritance. Confused, Fell teams up with Maggie, a plain girl with a similar background, to investigate the source of the riches. But what they find is a closet full of skeletons....

ESPECIALLY WHEN IT COMES TO MURDER.
Is it really possible Fell's father was involved in a long-ago train robbery? Who's the mysterious woman in, the portrait hidden in his mother's wardrobe? As Maggie and Fell poke around the village for answers, they find themselves on a surprise-filled path to danger and adventure, and--just possibly--love. But Fell's sudden good fortune could come to an abrupt end if he doesn't stay one step ahead of a cunning killer...