When 133 slaves are thrown off a slave ship after its water supply runs low, Garrow takes on the brutal slave trade that regards human beings as cargo when he is employed by Liverpool Assurance to prosecute the ship's captain for a fraudulent claim of £4000 for loss of cargo. He is aided by anti-slavery campaigner Gustavus Vassa. (In history the insurance company also refused to pay out, but the captain died shortly after and so was not put on trial.)