hold out on

ChandlerのPLAYBACKを読んでいます。恐らく主人公と思われる私立探偵のMarloweは依頼された尾行を開始しました。
"Yeah, the sun's shining and our friend is no more on the lam than you are. She ate breakfast in the coffee shop which has a glass wall towards the concourse. She sat in the waiting room with a hundred and fifty other people. And she could have stayed on the train out of sight."
"I have all that, thank you. I'll get it to Mr. Umney as soon as possible. You have no firm opinion then?"
"I have one firm opinion. That you're holding out on me."
引用個所の最後に出てきた "hold out on" は知らない慣用句なので辞書を見ます。
・Oxford English Dictionary: informal Refuse to give something, typically information, to (someone).: He's holding out on vital information that we trusted him with.
・Collins Dictionary: (informal) to delay in or keep from telling (a person) some new or important information
探偵小説にはよく出て来そうな表現ですね。覚えなくちゃ。
"on the lam" は "3/11/2011" に取り上げています。