The watcher spies late into the night on the enviably cosy domesticity of the Titmuss household. The seemingly happy couple, the loving children, the ordered normality of it all strikes a deep chord in Lorna Gibson, so different is it from the emotional emptiness of her own existence.

But over a period of time, the watcher realises the Mrs Titmuss is no longer playing by the rules, and that her behaviour, if allowed to go unchecked, threatens to shatter the harmony of husband Cecil's life. And Cecil is a decent man, as Lorna well knows. He doesn't deserve such an ignominous fate.

So the watcher decides to turn observation into action, and save the Titmuss family from inevitable heartbreak. But how far is she prepared to go