How the Cossacks searched for Mona Lisa

Three Cossacks — the mighty Tur, the lanky Gray, and the small Oko — are resting on a hill when a time machine falls directly on their heads. It turns out it was built by Gray's grandfather, who used it to send a message from the past: he was in love with the Mona Lisa and is asking his grandson and friends to find it. Before the painting, though, they first have to find the grandfather himself — which means solving clues scattered across multiple eras of history. The road is long, but it ends well.