By the light of the lantern he held were his features visible, relaxing to a singular smile--the smile the man of determined spirit wears when he reaches a juncture in his life where this determined spirit is to feel a demand on its strength, when the strain is to be made, and the faculty must bear or break. 
His features relaxed into a singular smile - the smile a determined man wears when his spirit feels a demand on its strength, which it must bear or break. 