This film reminded me of others from the late '40's up to 1950, of "D.O.A.", in some ways, with its tense realism. The cold, merciless criminal mastermind played by Lyle Bettger was a (considerably) more balanced version of the sinister characters portrayed by James Cagney in "White Heat" or Richard Widmark in "Kiss of Death".
This is an early police procedural, with the railway cops working closely with the New York City police. According to Leslie Halliwell, "Naked City" -- which I've somehow managed never to see -- is the prototype for all the films of this type. The style eventually became overfamiliar, and very diluted, on television with shows like "Dragnet". "Naked City" cast Barry Fitzgerald unexpectedly as the lead detective, and he repeats that role here.
The two principal stars of "Union Station" are William Holden and Nancy Olson, who also co-starred in "Sunset Boulevard" this same year, 1950. Nancy plays Bill's conscience, constantly concerned that the interests of the kidnap victim don't get overlooked in the hunt for the criminals.
Holden is quite good -- he really started to come into his own at this time -- indicating more depth than was strictly required for the stalwart hero in a crime story. Bettger shows calculated menace. The two make worthy opponents.