Common Side Effects season finale ending explained: Do Marshall and Frances reunite?
The Common Side Effects season finale premiered on Adult Swim on Sunday, March 30, 2025. Bringing the first season to a close, the episode, titled Raid, picked up right where last week's episode left off, with the FBI launching a raid on Marshall and Hildy's mushroom business in North Carolina. However, things go horribly wrong.
Warning: Spoilers for Common Side Effects season finale to follow. Reader discretion is advised.
In the Common Side Effects season finale, viewers finally see Frances and Marshall reunite after spending the second half of the season apart. Additionally, the ending of season 1 lays a setup for what's set to come in future seasons of the show and how Marshall and Frances will be right in the center of it all.
Marshall and Frances plan on healing the world
In the Common Side Effects season finale, Copano visits Marshall's operation in North Carolina after being taken there by Amelia. While searching for Marshall, he sees that Hildy is coming in from the woods and chases after Marshall. There, he finds his lifeless body and feeds him the mushroom, hoping to bring him back to life.
Before he does, Marshall can be seen in a void where he is somehow able to communicate with Frances and draw her a picture of a specific location. Marshall then wakes up, and Copano gets him a car and asks him to drive away as the FBI begins their raid. Frances, who is in a business meeting, gets up and leaves as well after seeing the picture that Marshall drew, and this leaves Rick confused.
Rick tries calling Frances, but she tells him that she is never going to work for him ever again, and this is the last he is going to see of her. By the end of the Common Side Effects season finale, Marshall and Frances finally reunite after finding each other in the same place, making a promise to heal the world together.
So, going into season 2, it looks like Marshall and Frances are going to be working together to grow the mushrooms. Additionally, it looks like everyone who may have taken the mushroom might be able to communicate with each other somehow. This seems to be a major plot point as well that fans can expect to see further fleshed out down the line.
Copano ends up having the mushroom too
During the FBI raid in North Carolina, after saving Marshall, Copano gets caught in the crossfire. Trying to save himself, he sees a toppled car; inside is Harrington, who had been leading the raid with the FBI. Seeing that she is injured, Copano rushes to save her and tries to get her out of the car.
Meanwhile, a helicopter with an attached machine gun is seen to be roaming in the background too, and it opens fire on the base. Amidst that, Harrington is shot as well, and Harrington wakes up to see her ex-partner lying unconscious. The episode then cuts back to Copano in the hospital and Harrington coming to visit him.
While Copano is hooked up to life support, Harrington takes a mushroom out of her pocket and feeds it to him. He suddenly starts getting better, but Harrington leaves before he can see her. At the end of the episode, Copano can be seen doing fine, while Harrington has fully joined the FBI. She is attached to the case of Marshall and Frances and is riding out into the desert to find them.
What happens to Jonas in Common Side Effects season finale?
In the Common Side Effects season finale, Jonas arrives in North Carolina and immediately starts asking about the mushroom. As he doesn't have much time left on his hands, he continues to get desperate. As the raid begins and chaos ensues, the mushroom inventory is left open. Jonas storms in and ingests multiple mushrooms at once, making him faint.
He then has a vision where he is greeted by the tiny beings. In his vision, he constantly sees his body continue to get worse and worse. He watches his body in various horrible shapes, where he keeps vomiting an even more mutilated version of himself. By the end of the episode, it is revealed that his condition has only worsened, and he is put on life support.
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Rick makes a pivot from pharma
In the Common Side Effects season finale, Rick makes a huge industry pivot. When Frances ends up leaving him, he is out of options on what to do since she was the face of the brand they were building. However, he is notified by someone that the mushroom works well with food as well since it has a flavor kick to it.
He then launches his brand of food flavoring known as Sparkl and becomes successful with it.
Other highlights from Common Side Effects season finale
At the end of the Common Side Effects season finale, viewers get to see a montage of what's happening with other characters as well. Amelia is shown to be alive, hiding from FBI agents alongside her son, Wyatt. A funeral is held for Rusty, who died fighting the FBI during the raid.
However, the biggest reveal comes when Zane finally receives a shipment of tortoises from Peru, with boxes full of them. Meanwhile, Hildy is seen putting a liquidified version of the mushroom into a town's water supply.
The Common Side Effects season finale is available to watch on Max right now.
Also read: 8 Shows to Watch If You Liked Common Side Effects
