As the threat of war looms over Europe in 1938, tensions simmer below the surface of the Cazalet family.
Villy gets pregnant and meets her husband's mistress, while a heart attack has romantic repercussions for Zoe.
As the Second World War is declared, Zoe gets pregnant and Rupert joins the navy. Meanwhile, Sybil is becoming seriously ill, but Edward's affair shows no signs of ending.
Clary searches France for her father, Sybil is taken into hospital and Louise meets an officer at a society dinner.
With no news of Rupert, little Neville runs away to Ireland. Meanwhile, Louise falls victim to her father once again.
Diana tells Edward that she's having his baby while Louise prepares for Michael's first visit to the family.
