Forbidden Places by Penny Vincenzi

Grace Marchant marries Charles Bennett at the beginning of the second world war, and loses him before she has really begun to know him-or even herself. In the five years while he is away, she makes her own life, on her own terms, and finds a new love, overwhelming and exciting in a way that her relationship with her husband never was. The return of Graces husband not dead at all, but very much alive-not only presents her with the most agonising of dilemmas, but brings to light many things which would have been much better left in the dark.....