Why so long at the tracks AFTER finding jewelry?
When they went back out to find the jewelry to bribe the guard to let the guy go, it was dark. When they found it, it was still pre-dawn. When she finds it, she and her son embrace at the tracks A LONG TIME!!!!
By the time they go back into the station, it's daylight - WTF? What made them dilly dally? The guard told her to hurry, he didn't have all night.
When they FINALLY return from JUST OUTSIDE the station, the night guard is gone and the day guard is there and they've sent him off to jail somewhere else!
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Before I get all wrapped up in the fact that it's their fault he was caught and sent to jail, due to the boy running off, her not getting her butt on the train sooner and then them having a reunion on the tracks...
Would the guard have just let him walk out of the station? Probably not, but she and her son seemed a little slow on the draw and even though they behaved so DESPERATELY, neither had a real sense of urgency in improving their situation...