Night Tiger by Yangsze Choo

In 1930s colonial Malaya, a dissolute British doctor receives a surprise gift of an eleven-year-old Chinese houseboy. Sent as a bequest from an old friend, young Ren has a mission: to find his dead master's severed finger and reunite it with his body. Ren has forty-nine days, or else his master's soul will roam the earth forever. Ji Lin, an apprentice dressmaker, moonlights as a dancehall girl to pay her mother's debts. One night, Ji Lin's dance partner leaves her with a gruesome souvenir that leads her on a crooked, dark trail. As time runs out for Ren's mission, a series of unexplained deaths occur amid rumours of tigers who turn into men. In their journey to keep a promise and discover the truth, Ren and Ji Lin's paths will cross in ways they will never forget.