Strangers Pass By On Heaven's Wings - The Unravelling, #1

Two young eighty year old apprentice scientific engineers, have spent years together trying to improve the performance of their matter transporter accidentally discover time travel.  They come from a repressive age and after being tortured, they agree to transport back to an age where a extremely despotic paranoid degenerate leader of his country can possibly be persuaded to help this future regime achieve its goal by changing history?  The period that they go back to is.1938!  They contact Adolf Hitler and ask for assistance.
Cruel, yes.  Funny, yes. Sad, yes.  Romantic, yes.  But most of all a book one of a trilogy that the reader will not be able to put down.