The answer is in the last line of the inscription on the front. "AVM deliver us from this evil".
This stone is a prayer, made more important by its being carved in stone. This is a terrified man's plea for help and is a rare insight into the Norsemen as humans.
Did they make it back home? I suspect so. They probably left before the water went down and made it back to their ship on the coast by a different route, avoiding the indians (Ojibwa?).
And that, I think is the story. Someone who is serious needs to get out to the knoll and start digging to see if they can locate other artifacts, such as datable ashes. It is a shame that this artifact has been treated so cavalierly over the years, as it could lead to further nderstanding of the Norsemen in Vinland.
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Why don't you just look up Hjalmar Holand's book on abebooks.com, his main work is Westward from Vinland, and he also wrote a few others, bet you could get yourself a real classic for a few bucks.