Dr Lambert pulled the incision open, and a bloodied circle of metal popped upwards, spinning. There was a visible spraying of tissue to highlight the fact that the gas was exiting under pressure. Red flecks spattered the walls and floor metres from the body. Whipping her head backwards, Dr Lambert instinctively put one hand to her mouth and pressed back down on the canister sticking out of the body with the other.

It took only a second for the horror to register in her eyes. She doubled over, her forehead hitting the corpse’s chest before she staggered back, grabbing for the table, a chair, anything to keep herself upright.

Ava looked away, put her own hand over her own mouth as if the gas were in the room with her too, steeled herself for what was to come and forced her eyes back at the screen.

Dr Lambert gave up trying to push the lid of the canister down. She was choking now, gasping for breath. The hissing had grown louder as the metal had emerged from the corpse. Dr Lambert crashed to her knees hitting the edge of a metal trolley as she went down. It shook but did not fall. Fate kept dealing cruel blows.

The small windows into the room were positioned near the ceiling to avoid passersby seeing in. The glass was thick to stop the sounds of saws from echoing through the building to where administrative staff or visiting families might hear. The room was effectively sealed to stop the stench of death from pervading the atmosphere.

Just maybe, Ava thought, if someone had been passing, the sound of a crashing tool cart might have attracted attention. But it wasn’t to be. Dr Lambert was on her hands and knees. Even with her limited view, Ava could see she was struggling to breathe. The temptation to rip off her surgical mask to get more oxygen must have been enormous, but Dr Lambert’s discipline was greater. She kept the mask on, one hand pressed against it. Did her best to crawl in the direction of the door.

Ava’s face contorted in fury. She put her hands up, clutching each side of the screen as if the image might escape, gritting her teeth.

Dr Lambert collapsed onto her side, knees drawn up, head thrown back, beginning to convulse. Spittle began to drip from either side of her mask, her eyes were swelling red. Her head flew from side to side as she fought the toxic gas. Finally, when she must have known she would never reach the door – probably knowing that even if she did, there was no way she would open it and risk the lives of her colleagues – Ailsa Lambert pulled the mask from her face.

Fighting her pain and her fear, she turned her head towards the camera.

Dr Lambert looked into the lens, shook her head, took a rasping breath and spoke her last desperate words.