I guessed that there would still be a number of invitation cards left over and that they would be in the secretary's room.

估计还有不少请柬， 应该在秘书室吧。

" Miss Keith, I didn't come here to smoke a cigarette with you, I came to snitch an invitation card and send it to Mr. Templeton myself" .

“基思小姐，我不是来找你抽烟的，我是来偷个请柬，亲自给邓普顿先生寄的。”

He was still holding the purloined invitation card and, thinking it incommoded him, I tried to take it out of his hand, but he tightened his grip on it.

他手里还拿着偷来的请柬， 我觉得这对他不方便， 我想把它从他手里拿走， 但他抓得更紧了。

This is not English, but French, and is normally seen on invitation cards. It just means, “respond if you please”, so you’d take it as an invitation to respond to whatever was asked of you.

(那个不是英文吧)这不是英文，而是法文。通常会在邀请卡上面看到 (像是婚礼邀请函等)。它的意思就是「若你愿意请回复」，所以你就可以把它当作一个邀请。