Where to Begin?

 The opening of a book is important - has to be in the right place. I'm pondering this at the moment for the WIP, 

It has three time lines - the heroine's, which is more or less contemporary with some back story. The historical mystery that folds around the whole thing, which begins just after World War Two. I have that one covered, as all is not revealed until the last third of the book. At the moment hero and heroine both start in the present but Nathan's story really begins six years ago, with a life changing event that has long repercussions. 

I'm now wondering if I should begin there, which raises the issue of writing a prologue. 

Prologues seem to be like Marmite, loved and hated in equal measure. I have read comments from readers who say they will not read them, and agents and publishers are said to hate them. The main argument against them seems to be that they are an information dump, loading the reader with backstory that would be better - and shorter - told as part of the main story. Prologue as tell, not show? 

Am I just info dumping? 

I've opened a book three times with events that take place before the main action, and it seems to have worked. I suspect that the new WIP will be the same as I seem to have got caught up in the idea, and it really is where Nathan begins. Actually, I suspect that it won't really be a prologue, it will be chapter one, because I can see it working out over a longer space than a prologue and introducing some major characters who feature later in the book - and it will be much better, I think, to introduce them in person  now than have to explain them later.  

So I will write it. This is the first draft, after all. We'll see if it works.