It is in a single-part form.

a (measures 1-8) + a1 (measures 9-16)

The key is G minor. The opening 8 measures begin in the low register, with both hands in the bass clef. The motif of the theme, in its first half, is played with an accented quarter note B accompanied by an appoggiatura, followed by three staccato quarter notes G, while the left hand accompanies with quarter notes forming an open fifth (root and dominant). In the latter half, ascending and descending eighth-note figures are repeated twice.

The overall impression of the theme is dark and eerie, and it also feels powerful due to the sound of the open fifths. This becomes even clearer when it is played an octave higher from measure 9.