English to Persian (Farsi) Art/Literary Poetry & Literature Colloquial Dialogue

Hi,

"So that's what this is all about!" here shows an ironic reaction to typically selfish behaviour, sometimes after one has erroneously believed for a time that a bad person has mended his ways.

This example will be familiar to some of you:

Supposing you hear that a young man who you know is very selfish is regularly visiting a lonely old man and giving him a great deal of help.

First of all you don't know what to make of it and you start wondering if you may have misjudged the young man. However, a friend tells you that the old man is extremely rich and, of course, when he dies, his money will be left to someone in his will.

You then say of the young man’s helpfulness, “So that's what this is all about!" ("So that's what’s behind it!")

Do you perhaps have an idiom for this like "پایان موضوع!" or maybe "پاین موضوع!"? I'm sure I heard something like this in a Persian-language film.

Best,

Simon