の件を

the matter of …

→ の
phrase Rare #36,394
the matter of … の links the matter to the preceding noun, and を marks it as the object of the following verb.
JA: その件を後で話しましょう。
EN: Let's talk about that matter later.

カムが三浦に工場の件を密告したから―二度と行くな

Because Cam tipped Miura off about the factory—never go there again.

— イップ・マン 序章 (2008)

お尋ねの件を調べました

I looked into the matter you asked about.

— 灼熱の魂 (2010)

女の件を尋ねてすぐ帰ったそうだよ

I hear he asked about the woman and left right away.

— サイコ (1960)