I can't seem to find this story anywhere on Google. The jist of it is
-They are hiking (in the US I believe) in the deep deep wilderness
-There is about 4 or 5 of them from the start
-Some sort of monster / beast is hunting them and kills all but 2 of them
-1 of them strays off for a day/days and comes back different
-The two of them are/were married (I think) but the man now acts differently b/c he became possessed or corrupted somehow.
-1 Guy ends up getting killed by the monster near a lake where the girl finds a boat and attempts to escape.
-The whole time she doesn't see the monster/creature until they are at the lake
-Presumably she dies too
That is all I remember and probably not enough detail, but worth a shot I hope!