A tremendously effective screen translation of Emlyn Williams' psychological frightfest, Night Must Fall is a classic nail-biter that, despite the passage of time, is still enormously effective. Primary credit is due to Robert Montgomery, who sheds his "light comedy" image with a finely crafted, carefully nuanced performance that grows more impressive with repeated viewings. That Montgomery can provide Danny with charm is no surprise; that he can do so in a manner that is simultaneously convincing to Dame May Whitty and contrived to Rosalind Russell is unexpectedly delightful. His understanding of the character's psychosis is impressive, and many of his choices -- the subtle changes in Danny's gait and stance, for example -- demonstrate the amount of care he put into this portrayal. Russell's part does not allow her the same range, but her work is polished. She makes the character's repulsion and attraction to Danny credible, which is crucial to the film's success, and her restlessness and discontent are pitched to exactly the right key. Whitty, of course, has a grand time; she and Montgomery are so believable that plot contrivances that might otherwise provoke grunts of disbelief are accepted without batting an eye. Credit director Richard Thorpe with guiding the cast through some difficult terrain; much of the screenplay requires finely tuned reactions and scrupulous attention to subtext to avoid seeming obvious, and Thorpe's careful handling sees that the tone of the scenes never strays into that pit.