BARNABY JONES -- Requiem for a Son ( pilot episode ) torrent

Barnaby Jones couldn't actually be considered a spinoff
from CANNON, since Buddy Ebsen didn't appear on CANNON until 1975.

Guest stars are William Conrad as Frank Cannon and Bradford Dillman.

Cannon and Barnaby worked together again a couple of years later
in the 2-part crossover episode "The Deadly Conspiracy".
Viewers had to watch both series to catch the entire story.