Ellipsism.

Alex and Ona have long since broken off their relationship. When everything seems to be over, Alex decides to come back into Ona's life by showing up at the home they once shared. As there is no one in the house, Alex decides to enter with the keys he still has. As he walks through each room remembering his past life, he hears the sound of the door: it is Ona, who does not know, yet, that their relationship was not broken for a simple matter.