'Mad Men' season finale set for Sunday

Reason to watch: Don's big sit-down (or showdown) with Conrad Hilton (Chelcie Ross) and much else.

Catching up: A pall has spread over the world, and the offices of Sterling Cooper, in the wake of JFK's assassination, while Betty (January Jones) appears on the verge of leaving Don (Jon Hamm) for another man. The daughter of Roger Sterling (John Slattery) still gets married, while dad reaches out to former paramour Joan (Christina Hendricks) after she had reached out to him for job suggestions. Pete Campbell (Vincent Kartheiser) is glum in the wake of a presumed demotion. Meanwhile, Sterling Cooper's on the block.

What Sunday’s about: No finale preview available — and no surprise in that creator and show-runner Matthew Weiner wanted to keep a lid on this one. The only clues are from this log line: "'Shut the Door. Have a Seat,' Don has an important meeting with Connie. Betty receives some advice. Pete talks to his clients." And yes, there may be a shocking end scene too — something of a departure for Weiner, who's leery of TV convention.

Bottom line: As cultural historians know, the JFK assassination was one of the great thunderclaps in American life. Pre-Nov. 22, there was hope, and post-Nov. 22, we were back in the land of fear and paranoia, with all roads eventually leading to the excesses of the '60s. Where will these roads lead in Mad Men? A palpable darkness settled over this glorious program's pitch-perfect third season last week. The darkness grows more visible this Sunday. How could we miss this spectacle? (We can't.)

Mad Men
10 p.m. Sunday, AMC