Doctor and Sarah deploy gas attack

Trapped in the basement beneath Solon's lab, the Doctor and Sarah scramble for a way to stop the Time Lord's resurrection experiments. Using his knowledge of hydrogen plant infrastructure and Sarah's discovery of a bottle of hydrogen cyanide, the Doctor devises a plan to disable Solon's operation. They combine chemicals to brew cyanogen gas, funneling it through the ventilation shaft into the laboratory above. The act cripples the lab's operations and halts Morbius' resurrection, forcing Solon to confront the consequences of his desperation. Their gamble buys critical time but tests the limits of their ingenuity and teamwork. key_dialogue: [ DOCTOR: HCN. SARAH: What? DOCTOR: HCN. SARAH: Ah ha! HCN. DOCTOR: Prussic acid. Good girl. DOCTOR: Stand back, Sarah. I mean well back. SARAH: Okay. DOCTOR: Something should happen. SARAH: How do we tell if it's worked? DOCTOR: Well, if we're still here in a month SARAH: It hasn't worked. DOCTOR: Correct. SARAH: Hmm. How many hours in a month? ]

Plot Beats

The narrative micro-steps within this event

3

The Doctor and Sarah search the basement for a way to stop Solon, with the Doctor using his knowledge of hydrogen plants to come up with a plan.

despair to hope ['basement']

Sarah finds a bottle of HCN, and the Doctor uses it along with other chemicals to create cyanogen, which they plan to use to disable Solon's laboratory.

uncertainty to determination ['basement']

The Doctor pours the cyanogen mixture into the ventilation duct, which should lead to Solon's laboratory, and they wait for the reaction.

action to anticipation ['basement', "Solon's laboratory"]

Who Was There

Characters present in this moment

2

Hopeful engagement evolving into cautious optimism tempered by dark humor — she believes in the plan but jokes to cope with proximity to death.

Sarah takes an active role, finding the hydrogen cyanide bottle and assisting the Doctor in locating and positioning the ventilation duct. She asks pointed questions, voices skepticism at first, then follows through with urgency. Her final line about the month’s hours shows mordant wit under pressure.

Goals in this moment
  • Help the Doctor identify and retrieve the hydrogen cyanide bottle
  • Trust his plan despite its risks and remain physically ready
Active beliefs
  • The Doctor’s intelligence can outmaneuver Solon’s sinister setup
  • Dark humor helps manage fear in extreme situations
Character traits
Resourceful searcher Quick learner of scientific terms Sarcastic under fire Loyal executioner of the plan
Follow Sarah Jane …'s journey

Focused intent cloaked in dry humor — he keeps fear and urgency carefully in check while orchestrating a dangerous gambit.

The Doctor works with urgent precision pouring liquids into a kidney bowl, then corralling chemicals and retreating to safety. His dialogue conveys calm authority masking the high stakes beneath. He kneels beside the duct, monitors the gas reaction, and exchanges quick, wry banter with Sarah while controlling the hazard.

Goals in this moment
  • Create and deploy cyanogen gas to disable Solon's resurrection machinery
  • Ensure Sarah steps back from the chemical reaction to avoid harm
Active beliefs
  • Chemical precision can overcome brute force and evil ingenuity
  • Safety margins must be respected even in life-or-death improvisations
Character traits
Calm under pressure Scientific improvisation Quick-witted strategist Concern for Sarah's safety
Follow The Fourth …'s journey

Objects Involved

Significant items in this scene

4
Hydrogen Cyanide Bottle

The small bottle containing hydrogen cyanide (HCN) is discovered by Sarah on the basement workbench. The Doctor identifies it immediately for its chemical notation and uses it as the primary reactant to brew cyanogen gas. Its clear liquid is poured carefully into the kidney bowl with prussic acid to create the disabling agent.

Before: Contained upright on the workbench, unnoticed among lab …
After: Emptied into the kidney bowl, transformed into cyanogen …
Before: Contained upright on the workbench, unnoticed among lab clutter — its lethal contents unknown to Solon’s team.
After: Emptied into the kidney bowl, transformed into cyanogen gas, then released through the ventilation duct causing immediate disruption upstairs.
Lab Kidney Bowl

The ceramic kidney-shaped bowl is repurposed as a chemical reactor. The Doctor uses it to mix hydrogen cyanide with another reagent to create cyanogen gas. After pouring liquids, he shoves the bowl into the ventilation duct, where the reaction releases toxic fumes aimed upward toward Solon’s laboratory.

Before: Resting upright on a side table, inverted by …
After: Partially melted and warped by the exothermic reaction, …
Before: Resting upright on a side table, inverted by the Doctor’s kick to reveal the duct beneath — now emptied of contents and repositioned under the duct grille.
After: Partially melted and warped by the exothermic reaction, its once-curved basin now indistinguishable from the spreading chemical fire it unleashed.
Side Table

The low wooden side table is inadvertently involved when the Doctor kicks it aside to expose the ventilation duct grille. Though it serves only as accidental cover for the duct, its displacement sets the sabotage in motion by revealing the escape route turned chemical delivery system.

Before: Stationary against the basement wall, slightly scuffed and …
After: Overturned and pushed aside, its sturdy legs barely …
Before: Stationary against the basement wall, slightly scuffed and unremarkable — holding no relevant lab equipment at the moment.
After: Overturned and pushed aside, its sturdy legs barely supporting it — now a minor casualty of the unfolding plan.
Ventilation Duct

The ventilation duct serves as the only conduit between basement and lab. It carries the newly created cyanogen gas upward toward the resurrection chamber. Its corroded grille and rough-cut metal frame accommodate the bowl’s placement, enabling the toxic cloud to drift directly into Solon’s workspace.

Before: Concealed behind a kicked-over side table, corroded and …
After: Clogged and fouled by chemical residue from the …
Before: Concealed behind a kicked-over side table, corroded and partially clogged with dust — revealed by Sarah’s inspection under the Doctor’s guidance.
After: Clogged and fouled by chemical residue from the gas, its function temporarily reversed from ventilation to chemical delivery system — now part of the sabotage.

Location Details

Places and their significance in this event

2
Serlano Institution Basement Complex

The basement acts as the staging ground for the sabotage. Its cramped, damp concrete environment becomes a laboratory of desperation where Solon’s discarded chemicals and overlooked ventilation infrastructure enable the Doctor’s plan. The flickering fluorescent lights cast jagged shadows over scattered cables and corroded pipes, all of which bear witness to the Doctor’s moment of scientific defiance.

Atmosphere Clammy, electrically charged with suppressed urgency and the stench of antiseptic mixed with ozone — …
Function Den of improvisation and chemical refuge
Symbolism Represents intellectual ingenuity surviving in the margins of evil’s infrastructure
Access Restricted to authorized personnel; must be circumvented to reach the lab above
Low ceiling pressing down on raw concrete walls Flickering fluorescent lighting casting jagged shadows Corroded pipes and exposed electrical wiring
Solon's Laboratory

Solon’s laboratory serves as the intended target of the cyanogen gas sabotage. The central resurrection rig housing Morbius’ braincase and artificial body is the operational heart of the evil scheme. As the gas seeps in through the faulty ventilation, alarms begin to blare and machinery fails, forcing Solon to abort the resurrection and acknowledge his experiment’s collapse.

Atmosphere Hectic and metallic, with burning ozone and the acrid tang of spilled chemicals — a …
Function Primary battleground of the resurrection plot
Symbolism Embodies amoral scientific ambition and the price of playing god with Time Lord biology
Access Controlled via locked doors and phased entry, though compromised by the ventilation flaw
Low beams flickering under electrical storms Green lamps casting shifting surgical shadows Central rig holding Morbius’ braincase wiring screaming hazards

Narrative Connections

How this event relates to others in the story

What led here 2

"Sarah's distressing dream about being blinded (beat_2179204cf49d4de4) foreshadows the later revelation that she was healed, paralleling the thematic contrast between destruction and restoration that culminates in the Elixir of Life."

Doctor explains Morbius threat and trap
S13E20 · The Brain of Morbius Part …

"Sarah's distressing dream about being blinded (beat_2179204cf49d4de4) foreshadows the later revelation that she was healed, paralleling the thematic contrast between destruction and restoration that culminates in the Elixir of Life."

Basement locked in desperate confinement
S13E20 · The Brain of Morbius Part …
What this causes 1

"The Doctor and Sarah's plan to release cyanogen into the lab (beat_88c7e24b5404873c) results in Morbius detecting the cyanide gas (beat_3ba8eabc39c3344e), escalating the confrontation between Morbius and Solon."

Solon’s gasping finality meets Morbius’s restitution
S13E20 · The Brain of Morbius Part …