Determined to uncover the secret, the king announced across the kingdom that anyone who discovered where the princesses went each night would be allowed to choose one as a wife and would inherit the throne after the king's death. However, he added a deadly condition: the volunteer must solve the mystery within three nights, or face execution. Soon after, a brave prince came forward, ready to accept the challenge. He was welcomed warmly and led to a small room connected to the princesses' bedroom. His bed was placed close to the door so that he could watch secretly and follow the princesses without being seen.
On the first night, exhaustion overcame him, and he fell into a deep sleep before he could discover their secret. By morning, the princesses had returned from their nighttime adventure, their shoes destroyed and heels worn through. The same fate befell the prince on the second and third nights, and he was executed without mercy. Many others tried to solve the mystery, but all met the same deadly end.
Eventually, a poor soldier, disabled and discharged from service, was traveling back to the capital. He encountered an old woman who asked him where he was going. He replied, "I don't even know where I should go." For amusement, he added, "I might as well try to find out where the princesses go at night, so I could become king." The woman smiled knowingly and told him, "It is not as difficult as it seems. Tonight, if you are offered wine, do not drink it and pretend to be fast asleep." She handed him a small cloak and explained that wearing it would make him invisible, allowing him to follow the twelve princesses without being detected.
Taking the advice seriously, the soldier sought an audience with the king and volunteered to solve the mystery. He was welcomed courteously, given fine clothes, and led to the guest room just like those who had tried before. That evening, the eldest princess brought him a glass of wine. Cleverly, he tied a cloth under his chin, pretending to drink while letting the wine soak into the cloth, and then lay down, snoring convincingly. The princesses heard him snore and laughed, confident that he would not succeed. The eldest remarked, "If he didn't drink, surely he would escape the fate that befell the others."
The princesses began to dress in dazzling gowns and adorn themselves in front of mirrors, eager for their nightly dance. Only the youngest princess expressed unease, saying, "I feel something is different this time. Something might go wrong." Her sister scolded her for being fearful, reminding her of all the princes who had failed before. Once ready, they checked on the soldier, who lay still and unresponsive. Satisfied, they proceeded to their secret passage. The eldest tapped her bed lightly, and it slowly descended into a hidden staircase. One by one, the princesses followed the eldest into the underground passage, while the soldier put on his invisibility cloak and silently followed the youngest princess.
Halfway down, he accidentally stepped on the youngest princess's gown, causing her to cry out in surprise. The eldest reassured her, saying it was just her dress snagging. At the bottom, the princesses emerged into a breathtaking avenue lined with silver-leaved trees that sparkled in the light. The soldier thought, "I need to take proof of this," and snapped off a branch, its crackling sound causing the youngest princess to shiver. The eldest calmed her, claiming it was the sound of celebratory gunfire.
They continued through paths lined with golden leaves and then diamond-like trees. At each stop, the soldier collected a branch as proof, while the youngest princess remained uneasy. Eventually, they reached a wide river where twelve boats awaited, each with a handsome prince ready to escort a princess. The soldier boarded the boat with the youngest princess. As the prince struggled to row, the princess noted, "Why does the boat feel so heavy tonight? Perhaps it is the heat." Across the river stood a magnificent underground castle, alive with music and glowing candlelight. Each prince danced with his princess, while the soldier joined the dance unseen, discreetly drinking any wine the princesses lifted to their lips. They danced until three in the morning, only stopping when their shoes were completely worn out. The princes then escorted them back.
The soldier returned to his room before the princesses, feigning sleep. The next two nights, he repeated the same strategy, taking care to collect evidence each night. On the third night, he even brought back a cup as proof. At the appointed time, he presented himself before the king, holding the branches and cup. Hidden behind the door, the twelve princesses listened closely. When the king asked where his daughters went, the soldier explained, "The twelve princesses dance each night with twelve princes in an underground castle." He described the entire journey and presented his evidence. The princesses, realizing the truth could no longer be hidden, confessed.
The king then asked the soldier which princess he wished to marry. He humbly replied, "I am no longer young. I wish to marry the eldest princess." The wedding was held that very day, and the king promised to pass the throne to him when the time came. As for the twelve princes who had danced with the princesses, they were cursed to live as animals for the same number of nights they had spent dancing. From that day forward, the mystery of the worn-out shoes was finally resolved, bringing peace to the kingdom.