SCDP is an independent agency still proving it can live without the old Sterling Cooper parent.
Don is divorced from Betty and ends Season 4 engaged to Megan Calvet.
Peggy is Don's essential creative counterpart after seasons of earned rank.
Season 4 is Don without Betty's suburban structure: therapy-adjacent collapse, work as identity, and Megan as reinvention fantasy with real affection.
Don's Whitman secret seeds.
Peggy rises from secretarial pool.
Betty marriage strain.
California and identity cracks.
Bobbie Barrett; Peggy's pregnancy secret path.
SCDP forms after London coup.
Betty divorces Don.
Kennedy assassination beat.
Don alone; Megan engagement.
Lucky Strike loss; firm panic.
Peggy as creative partner.
Season bridge: everything above is end of Season 4. S05E01 ("A Little Kiss (Part 1)") has not started.
Cutoff discipline: every fact above ends at S04E13. Do not import anything from S05E01 ("A Little Kiss (Part 1)") or later.