Having sung this song myself for aboout 40 years and done some translations of KK:s songs this is how I see it.
Casey's is entering the subway. He passes the turnstile and he hears the sound of chains. Could be his own key or watch chain or if Kris sings "the chain" it could be chains in the subway. There he starts thinking of the woman whom he just had been visiting, maybe an old flame, maybe a hooker he frequently uses. He'd probably go for her if he could but something keeps him from doing that. She's anyhow fond of Casey. Leaving the UG he feels he need a pint. He also need to kill some time as he don't want to go home. He's thinking so much about her, her being alone too, that he don't see others in the bar. When he's leaving he stumbles. Obviously he's in tears and maybe the beer is hitting his brain and he can't figure out which one was making him stumble. This would explain the song but the title is still a mystery to me.