In the opening scene, the cunning robber Diabolik expertly infiltrates a high-security jewelry company, Armen, aiming to steal the priceless Armen Crown. With only one guard on duty—while the others are distracted playing cards—Diabolik climbs through a window, neutralizes the patrolling guard, and reaches the crown's secure room. However, his actions set off an alarm, prompting the other guards to rush to the scene. They quickly discover they can't access the room because Diabolik has blocked the keyhole from the inside, leading to a tense standoff.