Alison is being honest with Vic about Aynsley's death, Mrs. S visits Dyad, and Rachel meets her father Ethan.
As Alison still grapples with the death of Aynsley, she finds a confidant in the wrong person. A preview for the next episode of "Orphan Black" shows Alison revealing to Vic that she committed a murder. "My neighbor Aynsley always thought she was better than me. ...Then I killed her," she bluntly says.
But Vic may not have a chance to tell anybody about this since he's seen collapsing into a craft room table with Sarah and Felix witnessing. "I may have spiked his tea," Felix says to a shocked Sarah.
In Dyad, Mrs. S pays a visit to Dr. Leekie. "I have something you want. It's your missing science, Dr. Leekie," she says. "What is it worth to you?" Meanwhile, Cosima and Delphine are having an argument, with the former saying, "This is my decision and not yours!" Delphine responds, "There is no decision, Cosima. You have one way forward, and this is it."
Elsewhere, Rachel finally meets her father Ethan, who recently told Sarah about Dr. Leekie's involvement in the death of Rachel's mother, Susan.
"Knowledge of Causes, and Secret Motion of Things" will air Saturday, May 31 at 9/8c on BBC America. According to the official synopsis, "When a rehab confidante betrays Alison and threatens to expose the truth about Aynsley's death, she goes into free fall on the eve of Family Day. With Donnie and the kids set to visit, it's all clones on deck to contain the fallout."
Co-creator John Fawcett recently talked about the return of Vic. "Well, Vic is a bit of a wildcard. Vic's always sort of showing up at inopportune moments and getting maimed for it. He's just a fun character because he kind of can bumble in at exactly the wrong time and wreak havoc," he told Entertainment Weekly.
"You have to see where that storyline is going. I think either way what is fun about Vic being in treatment with Alison is that we get to put those two together. Outside of what his other agenda is, if he has one, he and Alison kind of actually do sort of like each other."
Of whether Dr. Leekie is a good guy or a bad guy, he coyly said, "It wouldn't be fun if it was just a straightforward A to B to C connect the dots mystery, would it? There's a lot still to learn. I think the fact that Duncan is alive and is Rachel's father, essentially, is a big bomb to drop at the end, that Leekie is responsible for the lab fire that killed her mother."