The opening lines of Robert Frost’s poem “Desert Places” quickly establish the setting of the poem, while the falling snow affects different things in the first three stanzas of the work.
In lines 1-4, the speaker indicates that he is passing (or has just recently passed) a field that is filling up with snow, so that now
. . . the ground [is] always covered smooth in snow,
But a few weeds and stubble showing fast. (3-4)
In lines 5-8, the animals living in the field and/or in the nearby woods are increasingly covered by snow – “smothered in their lairs” (6). Note that the word "smothered" has ominous overtones that foreshadow the tone of the poem's final stanza.
In lines 9-12, the speaker imagines that the snow will fall even more thickly on the fields and animals and on the surrounding woods, so that they will be covered with
A blanker whiteness of benighted snow
With no expression, nothing to express. (11-12)
Presumably the observer speaker is also being covered with snow as he observes, although this possibility is not made explicitly clear. In any case, the lines just quoted suggest a kind of subtle nihilism, an emphasis on nothingness and on a lack of meaning. Paradoxically, the speaker gives vivid expression to a situation "With no expression, nothing to express" (12).
The third stanza thus suggests that the snow is not merely literal but is also symbolic. It symbolizes “loneliness” (9) and an absence of expression or expressiveness.
Finally, in the last stanza, the speaker makes clear that loneliness is not merely something that the landscape symbolizes but, far more important, a condition of the human soul. The poem progresses from an opening stanza that seemed to suggest a kind of external beauty to a final stanza that deals explicitly with fear in the soul, in the spirit. The poem has progressed from external to internal, from a literally deserted place to figuratively “desert places” (12), and from contemplation to a kind of dread.