Caveman

Newlyweds in college, recovering from a harrowing criminal case.
Asbjorn and Sean deserve a break. Since they never had their honeymoon, Asbjorn's karate teacher Nell offers them cabin in the back of beyond. Taking a canoe up there during spring break sounds like a brilliant idea.
An engineering major with his cell phone.
A rustic viking with his hunting knife.
Minimum supplies, no shelter.
What could go wrong?
Sometimes, only a trip gone pear-shaped reveals whether a couple is meant to last.

This "long-short" story fits right after Swordfall, book 2 of the Fall Trilogy.