This attracts the attention of a man named Adam Whitman, who shows up at Sterling Cooper and surprises Don.
Don feigns ignorance of who Adam is, and initially insists he is not Dick, the man's long-lost half-brother.
Adam, a janitor, is confused; later at a diner Don admits the truth, but he refuses to share any information about himself.
Don is then surprised by a call from his mistress, Midge, and Peggy accidentally overhears them making plans for a "nooner" (sex during lunchtime).
While Don is with Adam, Betty and the kids arrive for a family portrait, and a desperate Peggy, thinking he is with his mistress, has to cover for his absence.
[1] Andrew Johnston, writing for Slant Magazine, also praised the deepening of Don's backstory, and wrote that the series was finding its voice as "a comedy of manners".
Club in 2013, praised the emotional core of the story, but called the episode "over-obvious and [lacking] the subtext that really makes this show sing when it's working".