Diesel8: Maybe you don't want the other guy in?
Exactly. There was an A-320 incident in 2012 at JetBlue. Enroute from JFK to LAS the F/O became alarmed when the Captain began talking incoherently about "not going to their destination", etc. When the guy suddenly got up and went to the lav, the F/O got a deadheading pilot up front, locked the duty Captain out, made a P/A to have the F/A's and pax restrain the Captain, declared an emergency and diverted into AMA. The duty Capt was charged with interfering with a flight crew and eventually
found not guilty by reason of insanity. Great job on the part of the F/O and the F/A's.