As Thanksgiving approaches, Don's work responsibilities interfere with his domestic life. Peggy is given a new opportunity, provoking the ire of some of her colleagues. Betty makes a startling discovery.

The office scrambles without Don; Betty learns some disconcerting news.

The writers make an attempt to stave off late-night boredom during a mandatory overtime session. Roger throws a party as Joan and Greg host their own party. Sally has a run-in with Grandpa.

The firm celebrates as they hit a milestone. Peggy and Paul compete to secure the same account.

Peggy's taste in men proves questionable. Pete has to make a big decision about his career and a candidate makes a big impression on Don.