planning a powder/take a powder

Breakfast at Tiffany'sのHollyは服役中の年老いたギャングの幹部に毎週面会に行っていましたが、その事がそのギャングの組織への指令を伝える役割を果たしていたとして警察に捕まっています。FredはHollyの住んでいた部屋に行くとそこには別の男がいました。
He had a pretty face, lacquered hair, he resembled Jose; moreover, the suit cace he'd been packing contained the wardrobe Jose kept at Holly's the shoes and suits she fussed over, was always carting to menders and cleaners. And I said, certain it was so: 'Did Mr. Ybarra-Jaegar send you?'
'I am the cousin,' he said with a wary grin and just penetable accent.
'Where is Jose?'
He repeated the question, as though translating it into another language. 'Ah, where she is! She is waiting ,' he said and, seeming to dismiss me, resumed his valet activities.
So: the diplomat was planning a powder.
JoseはHollyと結婚する事になっていた外交官です。 "planning a powder" とは何でしょう。 慣用句かそれとも "powder" に私の知らない意味があるのでしょう。
"plan a powder" と言う慣用句は見あたりませんでした。　そこで "powder" を辞書で良く見ると "take a powder" と言う慣用句があり、上記引用文での状況にあてはまります。 "take a powder" の意味は辞書に次ぎの説明があります。
・Wiktionary: (idiomatic, US, colloquial) To leave in a hurry; run away; scram; depart without taking leave or notifying anyone, often with a connotation of avoiding something unpleasant or shirking responsibility.: "Mr. Tilton said you told him you would take a powder." "Take a powder?" said Henry. "I once heard a man from Nevada tell me he would take a powder, meaning he was leaving town."
・American Heritage Dictionary: To make a quick departure: “When he saw the police coming, the thief decided to take a powder.”
この "take a powder" の意味を知っていれば "plan a powder" はその変形だと気が付きますね。