Adding to Father O'Banion's troubles is the mission's cook Siu Lan, an attractive Chinese girl who makes no secret of her love for him.

Only after the villagers revolt and his superiors order the killing of all Christians, including his parents, does Ho San become convinced that communism will never solve China's problems.

He tries to smuggle Siu Lan, his son and the two priests out of the compound, but their journey is halted within a few miles of freedom by a helicopter sent to prevent Ho San's defection.

[9] They add that the final cut of Satan Never Sleeps was neither supervised nor approved by McCarey, "which may explain (if not excuse) the bizarre aspects of the film’s ending".

[10] Biographer Wes D. Gehring notes that McCarey had conceived a denouement different from that which the studio inserted, in which "William Holden’s priest dies, rather than act upon his love for a woman".

[17][18] Poague locates the weakness of Satan Never Sleeps less in its political metaphor for "personal and social rigidity" associated with Communist regimes, but rather a fundamental shift in McCarey's outlook that was "genuinely darker by the time he made the film".

McCarey presents families as "basic to the continuation of life and society" in a number of his films, among these Make Way for Tomorrow (1937), Good Sam (1948), My Son John (1952), as well as Satan Never Sleeps.