It was Junius's idea. They've been very kind to him, and as they were in Philadelphia...
5 seconds sound clip from the The Philadelphia Story movie soundboard.
You can hear this line at 00:20:04 in the Blu-ray version of the movie.
Quote context
[...]
- Rooms?
- Well, I'd better start from the beginning. Sit down, dear.
- You see, they're great friends of Junius's.
- They expect to stay here over the wedding?
- I think that's very queer indeed.
- I think it's queerer than that. I think it's paranoiac.
- It was Junius's idea. They've been very kind to him, and as they were in Philadelphia...
- You're lying, Dexter. I can always tell.
- But, dear, if they're Junius's friends...
- You went to work after the divorce, didn't you?
- Well, yes, except for a brief interlude in a couple of alcoholic sanitariums.
- But you took a job in South America. Who for?
- And it wasn't, by any chance, Spy magazine?
- You are a mass of intuition.
[...]