They arrived twenty minutes later, and with Miss Clark's permission, they went directly to the place the secret room was hidden according to their calculations. Sherlock knocked on the wall, which made a hallow sound.

'OH!' Mrs. Clark exclaimed. 'So this is where Mr. Smith hid the treasure! You found it, amazing! I never thought...'

'Mrs. Clark-' Interrupted her Sherlock. 'Could you do me a favor and stay silent for a moment?

He checked how big the walled passage was by knocking on the wall in different places.

'Three by five feet...' He purred.

Amber was analyzing the wall up close. It didn't look like there was anything hidden behind it. Whoever hid the entrance did it very carefully, because not only did they close the passage permanently, but also plastered and painted it with paint so that it did not stand out from the rest of the walls.

The girl tilted her head, thinking. Something was wrong. Someone tried too hard...

She touched the wall with her hand, examining its roughness. Then she walked up to the wall in the hall and touched it as well.

Sherlock, who had finished his examination, was now watching her behavior.

'When was the last renovation done here?' He asked Mrs. Clark, now understanding what Amber was up to.

'I have been working here for twenty years, and there has never been a renovation. Only Miss Smith's bedroom was repainted because it was very old and the young lady needed...'

But Sherlock and Amber no longer listened to her, rushing into Mr. Smith's former bedroom, which was adjacent to a hidden room.

If the house had not been renovated for twenty years, and the traces of the door to the secret room were not visible, there must have been...

'The second access to the room!' Sherlock whispered, pushing away a big wardrobe.

There it was. A small door, made of old wood.

'How come no one really discovered this for so long?' Amber doubted.

'Not all people are smart.'

She rolled her eyes, but Holmes did not notice, busy examining the keyhole.

'We need a small silver key, an old one, but...'

'Like this one?'

Amber gave him the key, the appearance agreeing perfectly with his description.

'How...?'

She smiled and pointed to the hook nailed on the back of the wardrobe he just moved.

'Not all people are smart.'

The detective opened a small door and went inside, leaning a bit because he was too tall.

But here was no treasure. There was nothing. The room was empty.

The only thing inside, lying on the floor, was a small envelope.

***

'You should be the one to read it. After all, it's your treasure.' Sherlock handed Miss Smith the envelope.

The woman looked at him suspiciously. She was calmly sitting in a chair in the living room, sipping tea, and here Sherlock and his assistant suddenly came and explained to her, one by one, that her father apparently hid the treasure somewhere else and left that envelope she was now holding in her trembling fingers.

She slowly opened it and took out a half-yellow card. She scanned quickly through the text of the letter, her face becoming paler by the second. She swallowed her saliva and began to read the letter aloud, not paying attention to the fact that Mrs. Clark was also listening:

"Dear Doris, I know you'll feel disappointed, but I couldn't leave the Aztec treasure in this house. I couldn't let General Homg take him over. It's been many years, but I'm convinced his desire to steal it from me has not weakened.

I hid the treasure so that no one would ever find it again. I hope one day you can forgive me.

Your loving father,

Hubert Smith."

She finished reading and an awkward silence fell in the room.

Amber stared at the yellowed piece of paper on which the ink was shining. This is the end of the search?

'Did your father ever mention what General Homg looked like?' Broke the silence Sherlock carefully examined Mr. Smith's letter.

'No... I don't think so.' Doris stuttered. 'But I think he had a pretty distinctive tattoo on his shoulder. I don't remember exactly; my father avoided the subject. I only saw their picture once and ...'

'Would you be able to recognize him now?' Interrupted her detective, now sniffing the piece of paper.

'I don't think so. This picture was a rather old one.'

'Interesting.' Sherlock interrupted her again and put the letter in her pocket, then turned to Miss Smith, who seemed more and more astonished by the moment. 'I believe that will be the end of my work here. The treasure is gone and I cannot help you anymore.'

Amber bit her lip. She knew Sherlock too well not to know he was up to something.

'So, goodbye.' said Holmes, and pulled Amber by the hand so quickly, she only realized when they were already outside.

'Why did you...' She started, but he was still walking, and not towards the street to catch a taxi. He took a quick step to the back of the house.

Amber followed him, curious about what he might be up to.

They went inside the house again, this time through the back door of the kitchen. Sherlock sneaked in quietly, and a slightly confused girl followed him. They stopped by the library and went inside.

She glanced at the huge book collection, but Holmes was already sitting at the wall, putting his ear to it.

She tilted her head, looking at him like he was crazy. He ignored her, listening.

Amber crouched next to her, thinking. From what she remembered, the library was right next to the staircase, the study, and the living room. Bingo.

She also put her ear to the wall. It turned out that it was very thin and she could perfectly hear conversations from the living room, including the distinctive high alt of Miss Smith's voice:

'... I still do not believe it. So it's lost for good?'

Mrs. Clark answered something, half whispering as if comforting her.

'...you have to tell him.'

'I will. As soon as he returns.' Miss Smith said. 'He went for a walk, you know.'

Sherlock sighed and stopped listening. He sat comfortably on the floor and leaned against the wall.

'All we have to do now is wait.'

'Will you at least tell me what for?'

He glanced at Amber, who sat next to him.

'It's very simple. You have the solution practically given to you on a silver tray.'

She made an offended face. She didn't like him messing with her because of her ignorance. She was not stupid.

'Really?' She replied, crossing her arms on her chest.

'Really. You just have to think a little.'

He smiled under his nose when she gave him a killer look. He reached into his pocket and handed her a letter.

'It wasn't Miss Smith's father who wrote it, was it?' She asked.

'What makes you think that?

Amber looked closely at the blue ink that covered the rustling paper.

'First of all, the handwriting.' She replied after a while. 'And after the freshness of the ink. This letter could not have been written earlier than a couple of days ago. And that means that...'

'That someone else wrote it.' Sherlock finished. 'Besides, the smell of the paper indicates that it was written near the kitchen, and Mr. Smith's bedroom was exactly on the other side of the part of the house where there the kitchen is, to which - as the master of the house - he never visited, so he could not write a letter in it. Even if he did not do it in his bedroom, but in his study for example, or-' He pointed his hand at the bookshelves around them. '-in the library, the smell that soaked in paper, is too intense. It must have been written very close to the kitchen.'

Amber looked at him, slightly blushing. Although he just proved that she did not see every clue there was, she liked to listen to his deductions.

'So someone wrote this in the kitchen a couple of days ago?'

'Yes, and, judging by the angle of letters, it was a left-handed person.'

Amber bit her lip.

'But why would anyone leave such a letter in a place where the treasure was hidden, if they took it in the first place?'

He did not answer, looking at her intensively. Suddenly she opened her eyes wide.

'So...'

They could hear voices in the living room again.

'...is not there. Neither are his suitcases. He couldn't...'

They both jumped up on their feet. They ran out of the library, and ran through the living room, ignoring the astonished cries of two women.

'We must find him!' Said Holmes, looking at the light of the setting sun. 'As soon as possible! We need to find Gerald von Hulimg he stole the treasure!'