Who killed the mayor in Silo?

The hand belongs to a Judicial security officer named Douglas Trumbull. The order came from above him, and the poison was probably never meant for her.

How she dies

Jahns and Deputy Sam Marnes (Will Patton) walk down to Mechanical to interview Juliette Nichols for the sheriff's job, and Jahns appoints her — over Judicial and IT, who wanted Paul Billings. On the way back Up Top the pair stop overnight at the Mids Deputy Station. At the end of episode 3, "Machines", Jahns collapses in her private bathroom, bleeding from the mouth.

Rat poison, in her water bottle. Marnes later concludes the bottles were tampered with during that overnight stop, and that the one that killed her was meant for him.

How Juliette works it out

Marnes is murdered in his own apartment days later. In episode 5, "The Janitor's Boy", Juliette follows the list of names he left behind:

• The planted evidence — she breaks into Patrick Kennedy's old apartment and finds a tin of rat poison and the pencil drawing of Jahns taken from Marnes's wall.
• The mistake — Kennedy moved out after his wife died, and Judicial's database was never updated, so the frame-up went into the wrong flat.
• The catch — Juliette hides Kennedy, then finds Trumbull at the door. He throws her over a stairwell railing and tries to prise her fingers off it. Bystanders pull her back up.
• The tidy-up — Trumbull reports to Robert Sims (Common) at a door marked JANITORIAL. Sims swears him in as his shadow, then pushes him over the rail. A suicide note turns up in his pocket.

Judge Meadows closes the case: Trumbull killed Jahns and Marnes, then jumped rather than be arrested. Juliette says out loud that she doesn't buy it and is told to leave it alone. Publicly, Jahns's death is attributed to heart trouble.

Who gave the order

Sims, at minimum. Before shoving Trumbull off the walkway he lists the man's failures — Kennedy, and George Wilkins, Juliette's boyfriend, whose death was also staged. Bernard Holland (Tim Robbins) becomes mayor pro tem within the hour and swears Juliette in himself.

The chain of command above Sims stayed deliberately murky for two more seasons. In "Farewell", the ninth episode of season 3, released on 28 August 2026, Bernard walks into the Vault and offers to confess publicly to killing Judge Meadows and to ordering the deaths of Jahns and Marnes, as a trade for Juliette's release. Whether that is a confession or a volunteer job as scapegoat, it matches what Juliette suspected back in episode 5. One episode of season 3 remains, "Troy", due on 4 September 2026.

For the record: Jahns and Marnes are buried together on the garden level, beneath a story Bernard invented about two colleagues finding love late in life. It was the only part of the cover-up that happened to be accurate.