Ranger Tim McIntyre is investigating a series of break-ins at private homes located within the boundaries of Rocky Mountain National Park that are closed for the winter. In one of these homes, a well-dressed stranger is found dead on the floor with his head in the fireplace, apparently suffocated by soot.

The investigation reveals that the dead man was a shady antiques dealer looking for a "lost" painting by Albert Bierstadt. A crooked restaurant owner in Denver is keen to acquire this painting. The dead man's partner takes up the search, and to throw others off the trail, she spreads a false rumor that she has found it but that someone has stolen it from her.

Although it means snowshoeing and skiing to remote buildings in RMNP, Ranger McIntyre sets out to search every cabin and lodge in his ranger district. But he is being followed by an armed thug, hired by the restauranteur. Luckily, McIntyre's classy-and capable-lady friend Vi Coteau and another park ranger named Eleanor Pedersen become concerned for his safety and decide to follow him into the mountains...