Before I Die — Helen McCloy

Kyra Novacs: Who was she? Where did she come from? Bob knew almost nothing about her, just enough to fall hopelessly in love with her. They were thrown together for business reasons and, believing her to be single, he threw caution to the wind.

But Kyra isn't single. And when her husband is killed in the midst of an argument over divorce, it falls to Bob's loyal wife of seventeen years, Susan, to prove his innocence ...

'Miss McCloy compels you to read every word' Observer