This story begins by describing a cosy domestic scene of a family inside their warm and snug house whilst a storm rages outside. A contrast is made through the safety and protection that the family have inside and the raging tempest that rattles against the house on the outside. Into this domestic scene an anonymous traveller, the ambitious guest of the title, enters. After relaxing, he feels that he is able to share his own desires and view of life with this family, and tells them about his ambitions:
The secret of the young man's character was a high and abstracted ambition. He could have borne to live an undistinguished life, but not to be forgotten in the grave. Yearning desire had been transformed to hope; and hope, long cherished, had become like certainty, that, obscurely as he journeyed now, a glory was to beam on all his pathway--though not, perhaps, while he was treading it.
What defines this stranger above all else is the ambition that drives him onwards and makes him believe that he will achieve some kind of "glory" in the future. This confession of the stranger causes the family themselves to open up and talk about their hopes and also their fears. Finally, the family hear a massive slide that they believe is coming towards them, and they all leave the house to run for safety, only to find that they run straight into the path of the mountain slide and all perish. Only the house is left, untouched by the slide. The message of the dangers of ambition and how it can cause us to put ourselves in the way of danger is clear.