The Onedin Line (1971) : 5x6

Letty tells James she invested in William's steam engine project and he buys a flour mill in her name, sailing to Pennsylvania to buy loose grain from an ex-Cavalry officer who drives a hard bargain. James gets what he wants after a drinking bout but the grain, known as dead man's cargo, starts to shift when the ship hits a storm and needs to be moved else the ship could capsize. A man dies in the process. Daniel and Elizabeth rekindle their old flame but their decision to tell William his true parentage proves to be unwise.