It was big news in Hollywood at the time that CANNON was leaving the air. The series may not necessarily have been cancelled, though the ratings dipped significantly as the series was running up against BARETTA, an overnight sensation. The show even left its long time Wednesday slot and moved to Sundays, taking the old MANNIX time slot.
The fifth season had some dynamic episodes and definitely could have had a longer life. There has also been some chatter that William Conrad may have bowed out due to personal reasons, and to note his wife passed a few years later. He may have wanted to spend time with his family. CBS certainly supported him, and thank you's were extended from all the good folks (and some superstars) who worked on the series.
The series is still around in reruns, which would have made him quite happy. In fact, it has been said that his later series, JAKE AND THE FATMAN was an offbeat salute to CANNON.
The final episode is quite good, all about controversial mind experiments in the US Army. Actually, beginning in the 1950s there were investigations as to whether military personnel were secretly fed illegal drugs. Later top shows such as 60 MINUTES and 20/20 did stories on military suicides and whether they could have been the result of subliminal drug activity.
Such is the case here as Cannon investigates strange happenings on an army base. The cast is top notch, with Conrad's old Warner Brothers pal Simon Scott playing a general, and looking every bit of the part. Soap opera star Quinn Redeker (DAYS OF OUR LIVES and THE YOUNG AND THE RESTLESS) plays Sgt. Wilson and versatile Peter Mark Richmon plays a colonel. Richmond was a staple in tv shows of the 60s and 70s.
Cannon did make a brief comeback in 1980 as a two hour movie, THE RETURN OF FRANK CANNON,
all about a mysterious murder on a ranch, which may have been inspired from an earlier episode that starred Julia Adams.
We will never forget Bill Conrad. When he passed in 1994, TVLAND saluted Cannon for years, not to forget the famous "Cannon diet" promotion. SEASON 5 EPISODE 25 remastered CBS dvd box set.