Despite my limited time in a spiritualist’s employ, assisting with setups and cleanups and as a participant when needed for a séance circle, I’d learned quite a lot. That included a stern lesson from Madame Esme that now both inspires and worries me.

“This is not to be careless with,” warned the turban-clad woman after I stumbled upon her bag of a chalky substance. Quicklime. “The smallest addition of water can scorch your precious skin.” Therein lay the secret to her illusion, I realized, of warming a glass orb to signal the presence of ghosts.

I’m counting on that ability again. Not pertaining to the ghosts, mind you, but as an effective source of heat. By lamplight at the desk in my room, I prepare to test my latest prototype. Mimicking the telescopic design of the Milk Can Escape, a soup can has been sealed in a larger tin. In the gap between them sits a measured amount of quicklime and, at the base, a compartment of water, potentially creating a self-heating meal.

It’s taken me several days to determine the ideal size and type of cans, plus the proportions of the contents. Luckily, Hutton managed to acquire plenty of quicklime for my attempts. Not a shock, I suppose. He possesses an exceptional ability to pull strings. Even my extended stay here at the George, a lovely old coaching inn located in Beaconsfield and just a half mile from Wilton Park, is by his arrangement.

I grip my bradawl, essentially a screwdriver with a pointed tip. Should this fail to work, I have a second sample to try, but no more. Any additions will take days to receive. The manager of a local cannery already granted me a favor by producing these so soon.

“Let’s make them count,” I say, hopeful.

Near the bottom of the tin, I poke two holes to puncture the water stall, keeping the quicklime safely contained—if my design holds up. I flip the gadget over and cautiously leave it on my desk. There’s a trickling sound but no visible leak. A good sign. Then comes hissing, the formation of calcium hydroxide.

My internal clock ticks away the seconds.

Five…ten…fifteen…

I recall my script from the stage: belief, perseverance, imagination. Sadly, that combination hasn’t yet been enough for me to outdo Hutton’s former right-hand man. When transferred overseas, the “charming, energetic, quick-minded” Peter Baker left an impossibly high bar, according to the major’s grating reminders: “Young Baker did this, Young Baker did that, and oh, another grand bit regarding Young Baker.” Plus, the military’s bureaucratic hurdles, often more so for women, haven’t helped my cause.

Gauging progress, I grasp the tin. I detect the water bubbling, the container growing warmer. “That’s it. Keep going.” Self-heating soup would be a feat in and of itself, but to achieve it in under a minute would be doubly impressive.

Forty…forty-five…fifty…