January Thaw (Murder-by-Month Series #9)

When Mira James moved to a small town in Minnesota, she thought she left muggings behind her... until she's jumped by two men in an alley. A third man saves her, but for all his trouble he's found frozen under an ice-covered lake. Meanwhile, Mira's job as a private eye in training has her tracking down the family that built the Prospect House, home of the town's new museum. Discovering a letter that dates back to 1865, Mira finds herself embroiled in a cold case of treachery and a hot case of drug trafficking that puts the whole town in danger.