Tim Williams has a happy marriage, a good relationship with his teenage son Max and the respect of his peers. Everything about his working and personal future is looking quite bright. The problem though: 15 years ago, Tim had a brief affair with the drug-loving Nat Manning. The affair ended in Nat finding out she was pregnant. After admitting this to his wife Christine, they patched up their marriage and fought hard for custody of the child. Nat moved to London and has hardly been heard from since. But now, 10 years later, Nat is back in their lives. This time for good.