About halfway through the story of Treasure of Nadia, you'll have to gain access to Sofia's storage room in the basement of her mansion. Unfortunately, the path is blocked by a security system equipped with laser beams. In order to proceed with the story, you'll have to disable the security system. This requires a three-digit numerical code. It's very easy to find, but most players will have missed it. You have already seen the required security system code serveral times while playing Treasure of Nadia. But to be honest, I didn't find the code myself while playing either.
To find the security system code you have to leave the building. Look around you. Above the balcony door of the mansion is the number 980. Could it be that this number is the code for the security system? A quick test confirms our assumption. We found the code to deactivate Sofia's security system.
Once you have entered the correct code, the security system will be turned off and the laser beams will disappear. You now have access to Sofia's storage room in the basement and can continue with the story of Treasure of Nadia.