"Requiem for a Son" is the first episode of "Barnaby Jones". Because this show and "Cannon" were both Quinn-Martin productions, it's not surprising they'd bring Cannon into the episode in order to boost ratings. Ironically, "Barnaby Jones" did quite well...lasting several more seasons than "Cannon"! And, incidentally, the pair would return in 1975 for a two-part episode...one of which was aired on "Cannon" and the follow-up on "Barnaby Jones".
When the story begins, an old friend of Cannon's calls and tells him it is important he see Frank as soon as possible. Cannon invites him to dinner...but the man never shows. It turns out he was murdered before he could talk to Cannon about his case...and Cannon learns of the man's death when he phones and talks with his father, Barnaby Jones. It seems that Jones retired some time ago but has come out of retirement to work with Cannon on this case.
When they start investigating, one strange thing turns up....that the dead man is not the only one close to a local politician who recently died. The politician's secretary reportedly committed suicide a few days earlier....and what are the odds?!
Overall, this is a very interesting episode--especially for kids of the 60s and 70s like me. The plot is good and seeing Jones and Cannon working together was pretty exciting...or at least as exciting you can get with a retired man teaming up with a very overweight guy to fight crimes! Well worth seeing.
By the way, Barnaby's daughter-in-law (the man who was murdered at the beginning of the show) later went on to be a regular on the show. Lee Meriwether played this role in this episode and throughout the series.