Two teenage boys flee from a moving train, shedding, as they run, long black coats that have the letters "KL" (the abbreviation for Konzentrationslager, which is German for "concentration camp") painted in white on the back.

In an out of sequence, non-consecutive series of dreams and hallucinations, the younger boy imagines traveling home to Prague by train and tram, walking around, passing two Nazi soldiers without incident, meeting a girl, and repeatedly ringing the doorbell at an apartment, all while wearing the coat that identifies him as a concentration camp escapee.

He struggles with thoughts of murder and sex, the film repeatedly showing both possibilities, but ultimately just silently takes the few slices of bread she offers and leaves.

As they walk away, the leader of the shooting party calls out, "Ready, aim, fire," but the old men merely clap and laugh and begin singing.

Lustig's obituary in The New York Times summarized "Darkness Casts No Shadow" as being about "two young men fleeing from a train and hiding in the woods.

[3] Antonín Kumbera, a Roma railway worker, was cast after Němec saw him in Evald Schorm's short documentary Railwaymen (Czech: Železničáři) (1963).

On review aggregation website Rotten Tomatoes, Diamonds of the Night has an approval rating of 90%,[4] with Eric Hynes of Time Out writing: "Němec’s technique is as emotionally intuitive as it is masterful, purposefully scrambling past and present, handheld realism (a breathless opening tracking shot) and Buñuellian surrealism (fever-dreamed ants colonizing Jánský’s angelic face).