S4, E7
You’re 4 seasons into this show, you’ve gotten to know a lot about Don and Peggy and seen their relationship evolve in huge and complex ways. And then this episode. It highlights all the worst and best parts of their characters and their relationship, and there’s more than a few all-timer lines and heart-wrenching moments. Spend one night with two characters who see each other in a new way by the time the sun rises.
Runner up from Mad Men: S3 E13, Shut the Door. Have a Seat.
It’s my favorite kind of conspiratorial drama, like a heist movie in the middle of a TV series.