YA book: agent with psi power, “pill” made of breadcrumbs

Question

I read this as a teenager in the 80s. It was possibly by Diana Wynne Jones, or a similar author.

The story involved some agents from an advanced culture helping out dissidents on a lower-tech planet ruled by a dictatorship. The agents knew how to access psychic powers that enabled them to do all sorts of things; crucially, though, this was something that everyone could learn to do with training.

One of the female agents was imprisoned with another woman, a citizen of the low-tech culture. They were both due to be tortured; the agent however would feel no pain under torture thanks to her psi powers. In an attempt to activate her fellow prisoner's own powers, she gave her some fake pills, actually just breadcrumbs, telling her they would make her immune but knowing that really they would give her the confidence to use her own inbuilt psi: basically, the same principle as Dumbo and the crow's feather.

This worked at first and the prisoner failed to suffer; there's a description of them acting as if they were in terrible pain, so that the torturers wouldn't suspect anything was up. However, before the next round of torture, the agent tried to give her some more pills, but failed to pretend to take them herself first; the prisoner refused to let the agent suffer. I don't remember how it was resolved.

Answer 1

You are describing The Far Side of Evil by Sylvia Engdahl.

From the pocket in which, providentially, I had hidden the remains of my bread from yesterday's breakfast, I drew forth two tiny pellets, pellets rolled from soft crumbs. They didn't look at all like bread to anyone who had been given no reason to suspect their origin. "Kari," I said levelly, "there's a means of protection, and I'm going to share it with you. You won't have to suffer at all. But you must go on trusting me; you must do exactly as I tell you and not ask questions.

She nodded, ready to grasp at the smallest straw of hope offered to her. "All right, then," I said. "Quickly, in case they come to repair the camera! Swallow this."

I gave her one of the pellets, eating the other myself with the greatest display of melodrama possible. She stared for a moment and then, trustingly, popped the thing into her mouth. "What - what will it do?" she asked in a small voice.

...

"...What will happen is that you'll find your mind working in different ways than it has before. For instance, you'll be able to communicate with me even when we're not speaking aloud. We've both taken it, you see, and we'll have -- well, telepathy."

For the next round, they did indeed run short on pills - and Elena, the Agent, was forced to take it by Kari, the Prisoner. However, because the effect of the "drug" was psychologically induced, Kari continued to experience the "protection" (italics == telepathy):

[Kari] Could [my mind have learned the trick?]? Not only for the telepathy, but for - for the [pain resistance], too?

I dared not give too positive an assurance, for however strong I made it there would be doubt in her, and the defense against pain is too elusive a skill to permit any doubt. I couldn't jeopardize her trust in me if I was to sustain her during the ordeals to come. Still, there was a bare chance.

Possibly, I hedged, if you go into this acting as if it will -- not letting yourself be afraid. You've nothing to lose by trying.

The character of Elena is more widely known from Enchantress from the Stars. The author has other sci-fi sets such as the Children of the Star trilogy and the much more recent "Flame" tetralogy which are both set (very broadly) in the same Universe but without any character or setting intersections (they all have small parts played by different Agents of the interstellar Service).