Domineering child Helena Vesey plans a lethal revenge on her childhood friend Maureen. As an adult Helena is excessively protective of her only child, Kit. When he informs her that that he is going to marry Angela, Helena feels abandoned. Having divorced her husband Alex soon after the birth of her son, Helena has believed for years that there has been no communication between Kit and Alex. However, Kit has maintained contact and is very close to his father, his step-mother and their children. When Alex helps Kit and Angela buy a flat, telling Helena proves rather difficult. News of Alex's Knighthood does nothing to quell her bitterness.
Ruth receives great media interest following a photographic exhibition and Helena is exceptionally jealous. When a documentary is made about Ruth's life, Helena discovers George's duplicity and orchestrates a suitable punishment.
There is an investigation into Ruth's death. George is devastated to learn he is to blame but remains adamant that it was not his fault. Angela wants to tell Helena about Kit's relationship with his father before she learns the truth from Laura. Alex becomes involved with a young American film actress. When he marries her, Helena sets her sights on destroying their happiness. Kit feels unwell and a visit to the doctor reveals some disturbing news.
Helena moves in with Angela while Kit is recovering in hospital. When Helena discovers Angela has been in contact with Alex, she feels betrayed. Helena bakes some lethal biscuits for Alex's picnic but they are not consumed by the person they are meant for. Kit's deception is exposed with dire consequences.