A is for Affection - between childhood best friends; between their parents; between brothers and sisters. B is for Broken-hearted - Natalie, when the boyfriend who was meant to propose dumps her just before Christmas. Her mother, when she realises what her life has come to. And Lucy, as she thinks of ending one relationship and maybe beginning another. C is for Chemistry - Could Natalie and Tom have it? And what does it actually mean, anyway?