This is book 21 in the 'Special Force Orca' series. The D-Day landings have just taken place, but do the Germans have a surprise up their sleeve? If the landings couldn't be stopped, what about the supply lines between England and Northern France? A force of U-boats is waiting in the wings to disrupt these latest convoys ferrying much needed supplies. Commodore Barr, as usual finds himself in the thick of things. This part of the storyline I found believable, but the areas dealing with 'Thule' seemed to stretch the imagination somewhat. Nevertheless if you suspend belief, it all makes for a good story.
Most of my favourite characters appear somewhere during the tale. The editing seems to be slipping again, but after so many books in the series it is not really that surprising. On the whole, it is still I series that I am enjoying.