At Dachau, an SS physician named Kurt Plötner spiked concentration-camp prisoners' coffee with mescaline and watched what came out of them. Some got giddy, some angry, some drowsy. He questioned them about their most intimate secrets, and he found they talked carelessly and openly. Sentiments of hatred and revenge against the guards, he reported, were exposed in every case.1
This is one of the ugliest experiments in a book full of them, and it earns its place for a reason that has nothing to do with its cruelty and everything to do with its finding. Because Plötner — a man with unlimited power over expendable human subjects, no ethical constraints whatsoever, and a drug that loosened his prisoners' tongues — reached the exact conclusion that every serious truth-drug researcher reached: it doesn't work. He wrote that despite the strongest doses of mescaline, "it is impossible to impose one's own will on another person."2
Sit with that. The Nazi doctor, of all people, hit the wall.
To understand why Plötner's failure matters so much, understand what an unconstrained test he was running. Every other truth-drug researcher in this book worked under limits — ethical review, the need for volunteers, legal exposure, the impossibility of reproducing real interrogation stakes in a lab. The Yale investigators had to use students who knew it was an experiment. The military studies couldn't ethically threaten their subjects with the consequences a real captured spy would face.
Plötner had none of these limits. He worked in a death camp. His subjects were prisoners he could kill and did — this was a man running lethal experiments on high-altitude, hypothermia, malaria, and cyanide. He could dose them without consent, question them under any duress, and discard them. If a truth serum were possible for anyone, it was possible for Plötner, who had removed every obstacle that constrained the legitimate researchers.
And he still concluded it couldn't compel the will. The drug got his prisoners talking — loosened, indiscreet, spilling their hatred of the guards. But talking is not the same as truthfully answering the questions the interrogator needs answered, and Plötner, watching carefully, saw the difference. "It is impossible to impose one's own will on another person," even with the strongest doses. The mescaline produced disinhibited chatter, not controllable, reliable truth.
Look closely at what Plötner reported, because it's diagnostic. "Decent persons remained decent during the examination," he wrote, "but it could be stated that mental restraints hardly occurred, sentiments of hatred and revenge were exposed in every case."3
Two things in that sentence quietly demolish the truth-serum dream. First: "decent persons remained decent." The drug did not override the subject's fundamental character or moral self-control — a person's core held, even disinhibited. Second, and more telling: what got "exposed in every case" was emotion — hatred, the desire for revenge — not information. The mescaline reliably surfaced the prisoners' feelings toward their captors, which is exactly what you'd expect from a disinhibitor: it lowers the guard on affect. But feelings aren't intelligence. An interrogator learns nothing operationally useful from the fact that a prisoner hates his guards; of course he does.
So the "success" Plötner observed — every prisoner exposing hatred and revenge — is actually the signature of the failure. The drug did the one thing disinhibitors do (release emotional restraint) and not the thing the interrogator needs (compel accurate disclosure of guarded facts against the subject's will). Plötner was honest enough, or clinical enough, to see that surfacing a man's rage is not the same as extracting his secrets, and that the will itself — the capacity to withhold, to resist, to remain "decent" — was not something his mescaline could break.
You are running the most unconstrained truth-drug test imaginable — no ethics, no consent, expendable subjects, a death camp for a laboratory. If a chemical truth compeller exists, you will find it. Here is what you actually get.
You spike the prisoners' coffee with mescaline, dose as high as you like — you have nothing to lose. You watch them loosen: giddy, angry, drowsy, their normal restraint dropping away. You question them about their intimate secrets and they talk, carelessly, openly. It looks, for a moment, like it's working.
Then you look at what they're giving you. It's emotion — hatred, the wish for revenge against the guards — surfacing reliably in every subject. But that's not intelligence; it's just the affect a disinhibitor always releases. When you push for the thing you actually need — their will bent to your questions, their guarded facts extracted against their resistance — you find the wall. The decent ones stay decent. The will doesn't break. What tells you the fantasy is false is that even here, with every constraint stripped away and the strongest doses in hand, you write in your own report the sentence every honest researcher writes: it is impossible to impose one's own will on another person.
The evidence is the intelligence report from Dachau itself — Plötner's own documented findings, recovered and cited. Dimsdale notes the report is "maddeningly brief," which is its own small tragedy of the archive, but the core conclusion is explicit and in Plötner's words.
The tension is a moral-epistemic one the book leaves deliberately raw: what does it mean that we cite a Nazi doctor's death-camp experiment as evidence — even evidence for a reassuring conclusion (that truth serums don't work)? Dimsdale documents Plötner without endorsing him; the finding is used, the crime is named. But it raises the uncomfortable question that runs under all the coercion research in this book: knowledge extracted through atrocity is still knowledge, and refusing to look at it doesn't un-extract it. Plötner's finding is real and it's useful and it was obtained by a monster torturing the helpless. The unresolved discomfort — that the cleanest disproof of the truth-serum fantasy came from its most evil pursuer — is left standing, because flinching from it would only make us less honest, not more clean.
Plötner is the darkest node in the network that includes The OSS Truth-Drug Committee — and the two form a grim convergence across the war's front lines. While Plötner spiked coffee with mescaline at Dachau, the Americans were spiking a gangster's cigarettes with marijuana in New York. Both sides, enemies in every other respect, independently pursued the identical chemical fantasy and reached the identical dead end: the drugs loosen tongues but cannot compel truth or bend the will. The war had two truth-drug programs, and they agreed on the only thing that mattered.
The convergence with Truth Drugs Don't Work: The Experiments is exact: the controlled Yale and military studies reached, under rigorous conditions, the conclusion Plötner reached under no conditions at all. When the ethical lab and the death camp agree, the finding is about as robust as evidence gets.
To behavioral-mechanics — Surreptitious Drugging as Control Vector. Plötner's coffee-spiking is surreptitious drugging in its purest and most unconstrained form, and it delivers the field's foundational negative result: even covert dosing of the utterly powerless yields disinhibited emotion, not controllable truth. The insight the pairing produces: the entire surreptitious-drugging enterprise — from Dachau to the CIA's Operation Midnight Climax two decades later — kept chasing a capability that its most extreme practitioner had already documented as impossible. The drug can make a person talk; it cannot make them obey or make what they say true. Every subsequent covert-dosing program was, in effect, re-running Plötner's experiment with better funding and worse honesty, and getting his same result while refusing to accept it.
To psychology — Suggestibility Under Extreme Stress. Plötner's observation that "decent persons remained decent" while emotion surfaced "in every case" maps the precise boundary of what disinhibition does. It lowers the guard on affect (feelings pour out) without dissolving the will (moral self-control and the capacity to withhold hold firm). The connection reveals why the truth-serum idea confuses two different things: disinhibition is not the same as suggestibility-to-the-point-of-compliance. A disinhibited person over-shares their feelings but retains their agency; a maximally suggestible person loses agency but then produces whatever they're led toward, true or not. Neither state gives the interrogator what he wants — one won't break, the other can't be trusted — and Plötner's report, read against the suggestibility research, shows the two failure modes are the only two outcomes on offer.
Sharpest implication: The cleanest disproof of the truth-serum fantasy came from its most evil pursuer. Kurt Plötner, with a death camp for a lab, no ethics, expendable subjects, and the strongest possible doses, found what every constrained researcher found: the drug releases emotion, not truth, and the will cannot be chemically broken — "decent persons remained decent." When the Nazi doctor and the Yale ethics committee reach the same conclusion by opposite roads, the conclusion is settled. And the settled conclusion is that there is no chemical key to the guarded, unwilling mind.
Generative questions: