The Clockwork Three by Matthew J. Kirby
When Giuseppe finds a green violin washed up in New York docks, somehow he knows it will change his life. But how? The very same day, Hannah, a maid at a local hotel, gets a strange new mistress. Why are Madame X and her mysterious Russian minder living in a hotel? What are they hiding from? Across the square, Frederick, a clockmaker's apprentice, hides his dark terrors, and an amazing gift. There is nothing to link these three children, except the green violin and a chance encounter on the street. But soon they are swept away in an epic adventure. This is a mesmerizing story of chance, friendship, and courage.