C-Man is a 1949 American thriller film directed by Joseph Lerner and written by Bertram Millhauser, which plays out as a classic film noir. Set in the late 1940s' post-war backdrop when the Cold War was building momentum, it grapples with themes of espionage, betrayal, and crime, quite typical of the film noir genre.

The movie centers around a mundane customs investigator named Cliff Holden, played by Dean Jagger, known for his Oscar-winning role in the 1949 movie Twelve O'Clock High. Holden is catapulted into a world of danger, deceit, and duplicity when he falls into a murder and theft case beyond his jurisdiction, giving the plot an intriguing twist. Jagger's portrayal of Holden, who is determined yet bewildered, reflects the profound character development typical of film noir.

The story begins with a customs agent being killed for a luxurious necklace he was entrusted with by the government. The murder turns into a theft as the priceless piece of jewelry also goes missing, the main plot conflict set in motion. Cliff Holden, being close to the victim, takes it upon himself to solve the case and recapture the lost necklace.

Holden dives deep into the mystery, where every clue unveils further complexity. Sundry characters weave the tale of intrigue and danger - with Harry Landers playing the cunning and ruthless antagonist Matt Royal, whose greed is the catalyst for the events of the movie. His character reveals the darker side of humanity hidden beneath a veneer of sophistication, further contributing to the film’s noir tone.

C-Man weaves a complex web of moral and ethical dilemmas typical of the noir genre, underscored by a palpable tension that runs throughout. The lines between vice and virtue blur as our protagonist navigates between friends and foes to solve the murder and theft.

The film also features actress Lottie Elwen, adding a feminine touch to the otherwise hardened scenario of the plot. Her character is multi-faceted, with palpable tension between vulnerability and courage, reflecting the classic femme fatale roles that were integral in film noir.

Accompanying the edgy narrative is the film's atmospheric cinematography which plays a significant role in enhancing the feeling of tension and danger. The use of dark and shadowy visuals, chiaroscuro lighting, and odd camera angles evoke a sense of uncertainty and hidden threats. C-Man thus successfully utilizes stylistic elements characteristic of film noir to immerse the viewer in the post-war era crime genre.

Director Joseph Lerner blends action, tension, and narrative skillfully to hold the viewer’s interest throughout. Despite working with a lean budget, the movie’s production value is impressive and sets a high standard for independent cinema of the era.

The screenplay by Bertram Millhauser, well-known for his contribution to the Sherlock Holmes series, is hard-boiled, chock-full with fast-paced dialogues, witty exchanges, and cryptic, cutting phrases - a hallmark of noir cinema that contributes to the movie’s thematic depth and narrative claws.

With an intriguing plot, complex characters, and unyielding suspense, the noir thriller C-Man captures the essence of post-war tension and societal unrest. Its blend of crime, intrigue, and moral ambiguity illuminates the darkness of the human soul while offering an engaging whodunit exploit.

C-Man appeals greatly to fans of classic film noir and those interested in post-war cinema broadly. This unique thriller holds power in its moody atmosphere, stark dialogues, and relentless tension, serving as an excellent example of mid twentieth-century crime drama that continues to be relevant today in its exploration of human motives and societal strains. Despite passing decades, it remains a relevant microcosm of anxiety and moral dilemmas sure to resonate with a contemporary audience.

In conclusion, C-Man is a must-see for those in pursuit of an intricate narrative, morally ambiguous characters, and suspenseful aura, all wrapped in the distinctive style of classic film noir.