Additional level

When walking around the city, a stranger bump you.
Apologizing, he runs away.
A little later, you notice an unusual item in your pocket.
Looking around him, you understand that this is a note that has been folded several times.
On a piece of paper a sign is drawn:
kracq xo cqdwmna bcxwn

Strongest sentence does not give you peace. Looking through the Internet, you will learn about the thunder stone, now part of the copper rider. It was found not far from Petersburg, after its excavations a lake was formed there. Now, Petrovsky pond.

Having searched this lake, you come across a small suitcase. Case has a three-code lock.
You got a call and a cold voice said: