In the season finale to Orphan Black’s fourth season, Cosima and Susan’s plan succeeded. With Kendall’s genome recreated, they now have a cure. Cosima tries to tell Sarah the good news before they’re disconnected, and she learns that Susan intends to use their work to resume cloning. After being informed of their success, Rachel gets an audience with the Neolution board and offers them new science by combining the recreated Kendall genome and Evie’s implant. They agree, but before they move forward something must be done about Susan.

Dr. Ian Van Leer, Evie’s personal physician, triggers her implant, killing her with a shot of toxin, making room for Rachel within Neolutiuion. After seeing Van Leer on television, assuming Evie’s role as head of Bright Born, Krystal contacts Felix who introduces her to Sarah. The idea of cloning doesn’t impress her, and she remains focused enough to tell them it was Van Leer she saw rescue Delphine from Dyad after Duko shot her.

With Cosima beyond contact and Rachel acting suspect, Sarah and Mrs. S kidnap Van Leer and learn that there are players beyond the recognized Neolution board, and they’re working on behalf of clones. They decide to hold on to him, and after finding Ira in a compromising position thanks to Ferdinand, Sarah arranges a helicopter ride to the island so she can confront Susan and rescue Cosima.

Susan, aware of the threat her daughter poses, arranges for Cosima and Charlotte to flee the island by boat. Before they can flee, Rachel returns to put her mother in her place and finds the man from her glitchy visions waiting for her. Susan reveals that he is P.T. Westmoreland, the founder of Neolution. Rachel can’t process her surprise before Susan, incensed at what her daughter had done to her sisters by promising the science to Neolution before manufacturing a cure, confesses that she regrets ever making her. It’s enough to push Rachel to stab her mother in the belly.

Cosima collapses in the woods with Charlotte in her arms, her illness preventing her from moving on. Approaching death, Westmoreland rescues the clones and takes them to his compound where Delphine tends to Cosima and saves her life. Cosima comes to and has her reunion with Delphine. She reveals that she’s stolen the genetic material from Rachel, and they can finally finish their work on the cure together. Delphine is pleased but cautious, and tells Cosima to keep their good fortune secret from those at the compound.

Sarah arrives to the bloodied house, ready to save Cosima. Rachel surprises her, beats her, and stab her. It takes a menacing gun in Susan’s hand to distract Rachel long enough for Sarah to limp away to safety. Alone on a dark beach, Sarah calls Mrs. S to tell her about her failure, but it’s Ferdinand who answers.

As far as season finales go, “From Dancing Mice and Psychopaths” was a perfect blend of fast-pacing, twists, revelations and warm reunions that’s capped off with a bittersweet ending that makes fans happy, sad and anxious over what’s happening to these characters. But as an end to Orphan Black’s fourth season, it’s just a reminder of what’s been a real mixed bag of great acting and frustrating storytelling.

There are quite a few issues I’ve had with this season, and the finale made them worse. Granted, the concept of an ensemble cast presents challenges for writers when considering which characters deserve the most attention. It’s made even more tricky when the premise of clones comes with an expectation of a big collaborative cast. Yet, this season has relied on contrivances to make certain clones take a seat. Like Helena running off to the woods for most of the season, or Krystal knowing about Delphine’s disappearance yet waiting two or three episodes at a time to fractionally deliver that important fact. It challenges logic and undermines the narrative, which would’ve been fine had it paid off. But I’m not sure it did.

After all the hype about going back to Beth’s origins and Bright Born being involved with Susan, nothing came of it. Evie was killed with a remote, making her the least problematic Orphan Black villain to date. Her henchmen were given much more to do in terms of shaping the narrative this season. So what was the purpose of her existence? The implant, which is set up to be incorporated in season five, Orphan Black’s last season, now that Rachel is on the board. But it hardly seems worth the effort to create a whole new villain and these sets of problems that in the end didn’t do much. A different vehicle to introduce these implants would’ve provided the room for a more engaging plot, one that made use of all the clones.

The more interesting bits from this finale connect to P.T. Westmoreland. Learning that Westmoreland is still alive and influencing his eugenicist secret society from his compound to the north inspires a great deal of speculation as to what science he’s working with and just how advanced Neolution’s methods of genetic engineering have progressed. There’s also the not-so-subtle hinting from Delphine that he’s not someone the sisters can trust even if Van Leer says he’s in support of the clones. For now, enigma is his strongest characteristic.

Now that we know Orphan Black is moving into its final season, and the issue of genetic disease is off the table, it seems the ultimate fight will be over the clone’s futures rather than just their immediate survival. Then there’s Neolution’s intent for humanity. But if the final season is driven by a throwaway villain, and the relationships between characters are ignored in favor of busy work, as was the case with this season, Orphan Black might end without making use of the formula that made it pitch-perfect sci-fi.