The Shadow in the North (2007) on Netflix

Plot summary

Sally Lockhart advises clients on investments and has done well at it, so when an investment she recommended fails, the client comes to her for restitution. The commodities went aboard a ship that disappeared on the high seas, and the insurers refuse the claim because of irregularities. Sally asks the ship's owner, Axel Bellmann, the richest man in Europe, for her client's money, and he turns her away. Her friends Frederick Garland and Jim Taylor have set themselves up as detectives, and she enlists them to find out what happened to the ship. Their inquiries reach Bellmann's other business: he is an arms merchant with a powerful new weapon, and he has bought his bride-to-be from an upper class family that is nearly bankrupt.