Hercule Poirot finds himself investigating the murder of his dinner host, Mr. Shaitana, who was stabbed in the heart while his guests played bridge.

A secret World War II document opens Elizabeth’s eyes to grim realities about a family member. The Duke of Windsor campaigns to re-enter public life.

When Elizabeth and Philip throw a grand party for their 10th anniversary, both Margaret and the new Prime Minister experience romantic tribulations.

Margaret and Peter are reunited, but another obstacle stands in their way. Elizabeth is torn between her duty as Queen and her love for her sister.

Margaret and Peter come to Elizabeth with a request. With a royal scandal about to break in the newspapers, the Queen Mother intervenes.

Elizabeth rejects protocol by appointing Philip to coordinate her coronation, but his ideas create conflict. The Duke of Windsor returns to London.

With Elizabeth in a new role, Philip tries to assert some power. Churchill wants to delay the coronation. King George’s disgraced brother arrives.