The idea that "Lamb to the Slaughter" suggests about encountering painful truths is that when these events happen in a person's life, as they almost inevitably do with everybody, they have a transforming effect on that person's character. Truths may be painful, but they are often valuable learning experiences. They often end up being liberating. This is illustrated in the painful truths that Mary Maloney encounters on a very important day in her life. The author, Roald Dahl, does not spell out the painful truths in so many words, but we can imagine what her husband tells her from Dahl's generalization and her reaction.
And he told her. It didn't take long, four or five minutes at most, and she sat very still through it all, watching him with a kind of dazed horror as he went further and further away from her with each word.
"So there it is," he added. "And I know it's kind of a bad time to be telling you, but there simply wasn't any other way. Of course I'll give you money and see you're looked after. But there needn't really be any fuss. I hope not anyway. It wouldn't be very good for my job."
For four or five minutes Patrick told her he didn't love her anymore. He was tired of her. He was tired of living in this house. He was tired of the sameness of existence. Tired of marriage. Tired of her slavish devotion. He told her bluntly that it was all over between them. There wasn't anything to discuss. He had thought it all over very carefully for a long time and he was going to leave her.
Mary, of course, was stunned. This came out of nowhere. She had expected it to be just another quiet evening in their orderly, conventional lives. She was going to be alone in the world with her baby. Her life was ruined. She didn't have anything to say in reply except:
"I'll get the supper," she managed to whisper...
She doesn't realize it, but she has become a different person. It isn't until she has that heavy frozen leg of lamb in her hand that she reacts to the "painful truths" she has just heard from her husband. She is not only different, but she sees him in a different light. Love can turn to hate--and it often does, though not usually as quickly as it does with Mary Maloney.
After she slays her husband, she shows she has become a different person by the way she goes about establishing an alibi. Since she no longer cares about her husband, she has to care about herself. She must actually feel cleansed of a lot of false illusions. This is what usually happens when we encounter painful truths in our lives. And the most painful truth we are likely to encounter is the truth that love is dead, if it ever truly existed--that the person who meant so much in our lives doesn't really care about us at all. There are always those who love and those who let themselves be loved.
Expectations of this world
And the people in it,
Are surely the sources
Of our greatest misery.
The Uddhava Gita #3