"The other man" Why not "another man"

English as a Second Language English Vocabulary, Grammar and Idioms
1

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,

Olga.

2

“Another man” could be any man.

“The other man” was referring specifically to Banderas.

3

Thank you for your help.

Best wishes,
Olga