To Steal
Because the hiragana ends with an う sound, you know this word is a verb. The kanji itself means steal, so the verb vocab version is to steal.
ぬすむ
What are you going to steal? How about a noose (ぬす)? Wait, why are you stealing a noose? That sounds like trouble to me...
あいつは絶対に中途半端なことはしない奴だから、3106カラットのダイヤモンドを盗むための壮大な計画を立てているに違いない。
He’s the kind of guy who never does something halfway, so he must have a magnificent plan to steal the 3106 carat diamond.