From the beginning, “Twin Peaks” has embedded a clue to unlocking the show in its title. David Lynch and Mark Frost are captivated by dualities, whether they’re giving their characters literal doppelgängers or they’re exploring the extremes of good and evil within humanity as a whole. What’s apparent on the surface counts for little in “Twin Peaks.” A homecoming queen from an upstanding family can turn out to be a drug addicted part-time prostitute, while her father can be a serial sex offender. Just because someone looks pleasantly familiar doesn’t mean they’re okay. Everyone is split.

This week’s episode is roughly divided into two parts, with most of the first involving the two current incarnations of Agent Dale Cooper — the addled insurance agent Dougie Jones and the vicious Mr. C — while the second part mostly catches up with a handful of the show’s original characters, back in Twin Peaks. In terms of driving the plot forward, most of the important business gets dispatched early. But what happens with the two Coopers subtly affects the meaning of the shorter, more scattered scenes in northern Washington.