You can download and play the game here:
Sneaking game
Please note that you'll need Adobe Flash player to use it. Sorry for the inconvenience.
Now, what to do? It's all in Russian! I know, I know.
You need to follow the first creature. When it looks back, click the mouse to hide. If the first creature sees you, it'll run away. If not, you'll get to the secret party!
You can't hide forever however, time is limited (see that candy on the right? It's the time tracker). Keep going and you'll get there!