Common Side Effects episode 6 ending explained: Does Marshall get to know about Frances' secret?

Common Side Effects episode 6 premiered on Sunday, March 2, 2025, on Adult Swim. Titled In the System, the episode followed Marshall as he was put into jail following the events of episode 5. Not only that, but the episode also saw Frances make a huge decision while Copano and Harrington faced a blowback.

Warning: This article contains spoilers for Common Side Effects episode 6. Reader discretion is advised.

In Common Side Effects episode 6, with Marshall being in jail, he finally gets to learn the truth about Frances and her working at Reutical. With this coming as a massive blow to him, Frances also makes the big decision of taking the mushrooms to Reutical, which is surely set to come as another shock to Marshall.

---

What big decision does Frances make at the end of Common Side Effects episode 6?

Frances after Marshall's phone call (Image via Warner Bros. Discovery)

When originally reunited, Frances didn't tell Marshall about where she was working. However, she kept grappling with the fact that if Marshall's mushrooms indeed did work, then what would she do with that information. Knowing that the mushrooms did work, she did try telling Marshall to take it to Reutical, however, knowing that he is against the company, she continued to play coy about her job.

In Common Side Effects episode 6, she meets her mother who tells her to take the mushrooms to Reutical as the situation is bigger than her and Marshall. She visits Marshall in jail and tells him about the idea, but Marshall refuses and tells her not to do anything with the mushrooms until he gets out. She then sees the statistic of how many people Reutical has helped and decides to pull the trigger.

She ends up taking the mushroom to Rick, and she tells him that she wants a promotion and never wants to worry about money ever again.

---

Marshall learns the truth about Frances

Marshall in Common Side Effects (Image via Warner Bros. Discovery)

This ultimately leads to Marshall receiving a big blow too in Common Side Effects episode 6. After ending up in prison, Marshall tries his best to get bail but is refused as forces beyond him still want him to be in jail. He ends up, however, getting on the good side of the prison king known as Christopher after he cures his cellmate of drug withdrawal.

During his stay in prison, Marshall is then visited by Heldi, who tells him to look into Frances and that she is lying to him. He is haunted by what Heldi tells him and decides to investigate for himself. Borrowing the prison cell phone, he makes a call to a Reutical helpline and asks for Frances and is redirected to her.

Disappointed by the discovery, he keeps the phone. Frances also realizes that it was Marshall who called her as she hears the prison bell go off. However, bad times for Marshall just don't end here as another assassination attempt is carried on his life. But before anything can happen, the episode ends up rolling the credits.

However, fans shouldn't worry about Marshall dying so soon because it was already confirmed by the mid-season trailer that he will be alive for the remainder of the show.

---

Copano and Harrington are split up

Copano and Harrington in Common Side Effects (Image via Warner Bros. Discovery)

Common Side Effects episode 6 also sees Copano and Harrington being split up. After their initial investigation, they are called up in Washington to meet with Cecily, who wants a brief on what they were able to find out about Marshall and the mushrooms that he has been growing. While they still remain unclear about Marshall's goals, they reveal that he was arrested by the police and is in jail.

When Cecily asks them about what happened to the mushrooms, they tell her that it's probably with Frances, as she was there when he got arrested. This leaves Cecily quite frustrated, and the case is shut down. Back at the DEA headquarters in Common Side Effects episode 6, Copano and Harrington get to know that they are being split up and put on different cases with different partners.

For further updates on Common Side Effects, be sure to stay tuned with us.