"The other man" Why not "another man"

I will be very thankful if you explain to me this question.

On Saturday I was waching the film with Antonio Banderas, who played a lover of
a married woman.
Why the director had used “The other man” and not “another man”?

Best wishes,


“Another man” could be any man.

“The other man” was referring specifically to Banderas.

Thank you for your help.

Best wishes,