"Our brave heroes flee the oncoming avalanche. They flee for their very lives, but still it's coming. Suddenly, an abyss yawns at their feet. Escape is impossible. "Well," one of them says, "I guess this is the end of the line."
(Of course, them being heroes, they surely make good a daring escape, probably utilising basejumping/snowboarding/other extreme sports)
That's "the end of the line."