The old villa at the end of Kwiatowa Street had been arousing the curiosity of all residents for years. For Lena and Bartek, however, it was above all the site of countless summer adventures. Ever since his grandfather disappeared under mysterious circumstances a year ago, the house had stood empty. This year, the first days of July were particularly hot, and the siblings decided to take another look at their grandfather's workshop. The door creaked loudly and streams of light danced on the old shelves full of tools, drawings and sketches. Lena reached for a dusty map she found on the desk as Bartek tried to move a heavy bookcase in the corner. Suddenly something fell to the floor with a bang. - I found something! - exclaimed Bartek, picking up a small metal box. They opened it together with trembling hands. Inside lay a watch that looked completely different from the ones they knew - it had a pulsating blue display and a dial with strange symbols engraved on it. Lena looked at it carefully. - Maybe it's her grandfather's prototype? - she wondered aloud. Bartek, always more impatient, pressed the red button on the watch's envelope. The room was illuminated by a flashing light, and the familiar sound of old church bells rang through the window.... only the sound sounded slightly different, as if it came from a very long time ago. The door in the studio shook, and Lena and Bartek felt a violent jerk. Everything around them began to blur, the walls seemed to melt into the air. One moment they were standing among their grandfather's familiar furniture, and the next they were somewhere else entirely. Bartek tightened his hand on Lena's wrist. In front of them was a view of a town that looked as if it had been transported to the past. People were pushing wooden carts, the streets were bustling with life.... But the strangest thing was that right next to them, in the middle of the market square, someone very much like her grandfather was leading a crowd of children towards a tall clock. Lena held her breath. - Is that really him? - she whispered. Bartek was already moving towards him when suddenly the watch on his wrist flashed brightly again. They did not yet know where this would lead them. Nor whether meeting his grandfather in the past would change something forever....