Voir Sadisflix. Birthday is a film about a group of teenagers who find a bizarre way for entertainment. One rainy evening, Marko and Kecko join in to celebrate Milan eighteenth birthday. It starts as a typical birthday party in which they indulge in hedonism and vices. Knowing that Milan is still a virgin and is desperately in love with their class teacher Nevena, Marko decides to make him an offer he can not refuse.