At the barber shop, a rival ad man congratulates Don for landing the Jaguar account. "This is a big win for your little agency," he says.
Lane has breakfast with a member of the 4A's, who praises Lane's fiscal track record and asks him to serve as head of the association's Fiscal Control Committee. Lane accepts.
At a partners meeting, Pete says Jaguar would like to pay SCDP via a fee structure instead of straight commission. He adds that Dunlop – Jaguar's tire supplier -- is interested in meeting with SCDP.
As Betty packs for a family ski vacation, Sally complains that she'd rather spend the weekend with Don and Megan. Betty calls Don to say she's dropping Sally off, seething that "It's your child bride she wants to spend time with."
Examining the company financial records, Cooper finds Lane's forged check and accuses Don of giving an unauthorized Christmas bonus. Don says he'll take care of it.
Don calls Lane into his office and shows him the check. Lane protests at first but then apologizes and tearfully argues "that was my money." Don demands Lane's resignation and gives him the weekend to think of an "elegant exit." When Lane says he feels lightheaded, Don assures him "that's relief" and "this is the worst part" of starting over.
Lane shows up drunk at Joan's office, but she sends him away after he makes a lewd comment. He retreats to his office, downing his drink.
Declaring that he's tired of "piddly" accounts, Don tells Roger to arrange a meeting with Ed Baxter at Dow Chemical. Roger calls Dow the "Moby Dick" of accounts and reminds Don that Ken is squeamish about doing business with his father-in-law, but Don is unfazed.
To Megan's surprise, Sally shows up at the Draper apartment and informs Megan she'll be staying for the weekend.
Over drinks, Roger tells Ken they're going after Dow Chemical but assures Ken he's not obligated to work on the account. Ken agrees to keep the proceedings secret from his wife if Roger agrees to "force" him onto the account - and to exclude Pete from all meetings.Roger tells Don he arranged a meeting with Baxter on Monday.
Megan lights into Don for not telling her about Sally's visit. Don confides that he had to fire Lane for embezzling.
Lane arrives home drunk to find that Rebecca has surprised him with a new Jaguar. "You never spend on yourself," she says. Lane vomits but the next morning reassures Rebecca that he likes the car.
While Don prepares for the Dow meeting at home, Sally joins Megan and her friend Julia for lunch. Megan asks Julia to tone down sex talk in Sally's presence, but Sally explains she has a boyfriend -- though she isn't sure he likes her "that way." Megan assures Sally that great romances often start as friendships.
Lane attempts to commit suicide in the middle of the night using the new car's exhaust, but the car fails to start.
Sally invites Glen to visit while Don and Megan are at work the next day. He agrees to sneak off campus and take the train into the city.
That night, Lane walks into SCDP's empty office and types a letter at his desk.
The next morning, Sally waits for Megan to leave the apartment before rushing to change out of her pajamas.
Roger gives Don a pep talk as they wait outside Baxter's office.
Glen arrives at the Draper apartment. He and Sally visit the Museum of Natural History. Glen admits that he told friends he was going to "do it" with her, but that he thinks of her as a little sister. Feeling ill, Sally runs to the bathroom and finds blood on her underwear.
Don brushes off Baxter's concerns about "that letter" and insists Dow Chemical needs a new agency, despite having of the market share. "I won't settle for of anything," Don says. "I want home, Megan looks for Sally and sees Glen's duffel bag.
Sally takes a cab to the Francis house and sprints to the bathroom. She hugs Betty tightly and explains that her period started and she didn't know what to do: "I just wanted to come home."
Scarlett drops off some company records with Joan, saying Lane hasn't arrived and his office door is locked.
Glen shows up at the Draper apartment and tells Megan that Sally left him at the museum. Betty phones and tells Megan that Sally "became a woman today," and "she just needed her mother." Megan insists Glen stay until she can drive him to his train.
At the office, Joan tries to open Lane's door but finds it blocked. She alerts Pete, Harry and Ken, who peer through the adjoining office window. "Dear lord," Pete gasps. Ken holds Joan as she bursts into tears.
Betty gives Sally a hot compress and curls up in bed next to her, assuring Sally that getting her period means "everything is working."
Back from their meeting with Dow, Don and Roger arrive to a nearly empty office. Cooper, Pete and Joan inform them that Lane hanged himself. Don forces his way into Lane's office and they lay Lane's body on his couch. Roger picks up a note from the floor and opens it. "It's a resignation letter," he says. Don closes his eyes.
At home, Don offers to drive Glen back to Hotchkiss. "Everything you think is going to make you happy just turns to crap," Glen says. Don asks what Glen would do if he could do anything.
Later, Glen drives Don's car and smiles as Don helps him steer.