Mad Men did it to me last weekend. It was the first time it had happened since the John Adams mini-series last year.

As a dedicated TV watcher, every now and then a scene floors me. Immediately there’s an epiphany: I will never forget this scene, as long as I live.

In John Adams, it was the scene when the title character, played by Paul Giamatti, meets King George III. Little was said, but the tension in their eyes was staggering.

Last weekend’s memorable scene in Mad Men — the Emmy Award-winning drama set in the early 1960s which has its third-season finale tonight on AMC — wasn’t notable for its tension, but rather for its deftness.

Harry Crane (played by Rich Sommer) is sitting in his office talking to Pete Campbell (played by Vincent Kartheiser). Pete has just been passed over for a promotion and he is worried about his future at the ad agency.

“What does it mean?” Pete asks.

“It’s not good,” Harry says.

Just as Harry is uttering those words, the flickering TV in the office flashes the word, BULLETIN.

The realization smacked me right away: Oh my God, this is when U.S. President John F. Kennedy gets assassinated.

Harry and Pete continue their conversation, oblivious for the moment to the larger drama unfolding. The familiar voice of Walter Cronkite competes for our attention, with words such as “Dallas” and “shots” and “motorcade” cutting through.

Knowing what we know now, it’s chilling.

The world is changing forever, but Harry and Pete are lost in their own drama. It’s not that they don’t care — once they realize what has happened, Pete, in particular, is very affected by it — but it’s a poignant picture of the way the world works.

Big news gets to people in different ways, at different speeds.

We immediately thought of a conversation we had with Mad Men creator Matt Weiner last January. He still was in a contract dispute and claimed he hadn’t written anything for Mad Men’s third season.

Mad Men is moving through the 1960s chronologically, but the show is about characters, not events. The dilemma facing Weiner was what to do when big things happen.

“Some of the events in the future from where the show is are so big, I don’t even know if I want to include them,” Weiner said at the time.

Well, as last weekend’s episode proved, he found a way. A big news event was incorporated, but Mad Men still was centred on its characters, most of whom found a way to reach out to the people who were most important to them.

Earlier this season, we did feel that Mad Men was spinning its wheels a little bit, plot-wise. That’s not to say we didn’t enjoy every minute, but the storylines were chasing their own tails.

The past two episodes, however, have been dynamite. There is so much to address in the finale tonight — particularly, are Don and Betty done?

As long as Mad Men isn’t done. It makes a present of the past.