More Fools' Gold — Bob Scott

Dispatched by his mysterious partner Helen, on an obscure mission to the far north of Scotland, Michael Scourie, together with his marine archaeologist daughter Sam and grandson Will are drawn into a dangerous world of spying & secrets.
Just 10 days later, a hunted agent forces them to aid his escape to France. There, they encounter a deadly foe, intent on a reckoning and their demise.
Faced with no other option, they have to commit a dangerous robbery and become criminals to save themselves.