Tragedy and violence
A lovely family of powerful, well-rounded people with good intentions quickly becomes a horror scene. First there was the war which leaves the girls without their hero, David, and which leaves Robbie with horrifying PTSD. Then to boot, it's the beloved who kills her lover, and the sisters betray each other for the man they conspire to kill. The constant trauma and tragedy underscores the random sadness of life and the difficulties of family and romantic love in a world where terrible things happen.
Post-Traumatic Stress Disorder
After the war, Robbie is left with shell shock, or PTSD. The condition is worsened by aggravated situations and loud concussive noises, and when Robbie freaks out in the final scene of his life, there are fireworks going off by the house and there's a gun. Robbie is upset because of Emmeline's selfishness, and he snaps. The result is his own death. It's a depiction of the horror of paranoia and the crippling effects of PTSD.
Confession and shame
One might question an old woman's decision to tell a dark secret that will tarnish her legacy, but that's exactly what Grace decides is best, given her entire life of reflection and thought on the matter. It turns out the suicide of the poet was actually violent murder committed in a moment of panic, spurred by the intensity of his own Post-War panic. Although she has shamefully kept the secret for her childhood friend, she now needs the clean conscience that confession will provide, in order to face her own death.
