Poll: The files sitting in the office that I was talking about yesterday are in disarray
- Votes: 150
- Comments: 3
- Added: February 2012
- Polls: 1,167
- Votes: 687,359
- Comments: 4,844
I was talking about the files yesterday
Subject-verb agreement applies.
The files .... are
If the office is the subject, it would be 'is in disarray'
Yesterday I was talking about the office in which the files are now sitting. (Non - native speaker, this is how I would paraphrase it.)