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Tear Jerker: Becker
One of the last episodes has Becker trying to get to Chamber Street, but is interrupted by a old woman on the subway who asks for directions. When he does, she gets confused, so he ends up taking her there, getting increasingly frustrated. Finally, when she gets there she can't go up the stairs from the subway. When Becker asks why, she says "he would've been forty." Becker then asks "who," to which she responds "my son." She then begins telling a story about how her son had talked to her, telling her what he had for breakfast, what he was going to do that weekend, that he had a meeting a few floors up, and how he could see all of Manhattan from his office. If you don't already know where this is going... she says it was a nice "September morning." Becker's irritation disappears and he lets her finish the story, and the episode simply ends with them sitting on a subway bench, him quietly holding her hand.
The end of the episode "Man Plans, God Laughs". While giving him a checkup, Becker makes a plan with a patient, Peter, to go to a hockey game after work. Just as he's leaving, having cleared up the chaos Linda created while covering for Margaret, Becker gets a call from Peter's secretary - he collapsed at his desk and died of a massive cerebral haemorrhage. The Mood Whiplash and Becker's clear guilt due to believing he missed something is what makes the scene.
The Series Finale features one of Becker's patients since Season 1 on his deathbed. The dialogue the two share gets me everytime. It's the reason I can never watch that episode...