Senate Intelligence Committee staff were investigating the Central Intelligence Agency's Bush/Cheney-era torture programs.*
The compromise agreement between the Intelligence Committee and the CIA regarding investigation-related documentation was for the CIA to provide a secure room with computers, a local network, and electronic copies of the millions of documents.
Among those documents were drafts of the so-called Leon Panetta torture review, which confirmed the Intelligence Committee's torture report conclusions and proved that the CIA lied to the Intelligence Committee about torture multiple times.
Without telling the Intelligence Committee and without permission, the CIA went onto the computers in the secure room and deleted files, including some of the Panetta review drafts, more than once. At some point the CIA also searched the computers and told the Intelligence Committee after-the-fact.
At some point Intelligence Committee staff took a copy of a Panetta review draft, redacted certain information from it according to standard protocol, printed it, and took it to the Committee's own secure room in the Capitol.
The Intelligence Committee has referred the matter to the Department of Justice for investigation into constitutional and criminal violations on the part of CIA officials.
The CIA has referred the the matter to the DoJ for investigation into crimes related to the handling of classified information on the part of the Intelligence Committee staff.
If we are to have a national government that operates under any semblance of the rule of law—if we are to have a legitimate constitutional form of government with separation of powers—if we are to have any pretense of a free country—then the Senate must win, and the Central Intelligence Agency must lose.
This would mean that high CIA officials would be up for potential prosecution and prison sentences.
The prospect is strong that they will not go quietly.