Only later, after flipping through her father’s files, is she reminded in a dream that the handsome ex-Marine Ben Cruz (Ramon Rodriguez), with whom her father appeared to be obsessed, had been hanging around her mother before she died — and may well have murdered her.

All of this takes place surrounding two sexual encounters between Joanie and E.J. During the first, E.J. stops everything short when he realizes that Joanie’s violent sexual proclivities may mean she inherited her parents’ trauma after all. The second takes place after Joanie admits to her husband, Paul (Lyriq Bent), that she has been serially unfaithful, seemingly to torpedo their relationship. According to E.J., this kind of behavior, and the despair that drives it, stems from never properly grieving the people she loses.

In a way, this episode feels like “The Affair” mourning its departed stars. Seeing Joshua Jackson’s open, soulful face as Cole in flashbacks; hearing Ruth Wilson’s ragged, bottomed-out voice as Alison in voice-over; watching Joanie wrestle with her memories of both parents as if those memories were living things she must defeat in order to survive … all of it draws attention to the enormity of the contribution those actors and their characters made to the show, and the void left in their wake. After half a season of the Solloways and their circle of lovers, friends and family, the Lockharts finally get their due, and it’s long overdue.

The show runs a major risk in putting its missing pieces front and center, of course: It highlights how “The Affair” is no longer about half the people it used to be about. If you miss them, well, you’re going to miss them even more after an episode devoted to how magnetic and fascinating they were.

And the shortcuts required to bring them back to the forefront are noticeable. E.J., for example, feels like a plot contrivance as much as a character: His mile-a-minute garrulousness and his job as an epigeneticist both feel designed to deliver as much exposition as possible in the shortest amount of time. That he and Joanie jump into bed together the same day they meet at her father’s grave site — a connection that feels forced — is partially explained by her serial infidelity. But a more convincing reason is simply that the writers, for whatever reason, decided that they needed this guy in order for Joanie to get to the bottom of her mother’s murder.