Wayne Rogers guest stars in this one. "Call Unicorn" begins with a trucker being murdered by a group of criminals within the trucking company. Apparently, they figured out that he's an investigator and they wanted to shut him up...permanently. Soon, Cannon is working at the same place--undercover and as an 18 wheeler driver! Oddly, apparently, Frank Cannon knows how to drive big rig trucks. However, to try to force the gang's hand and discover who their boss is, Frank plays it tough--very tough. This seems to be working when a monkey wrench is tossed into the works--the woman Frank is 'married to' (as part of his cover) is surprised when her sister shows up and wants to meet the new husband! This is a good episode--mostly because the plot is very unusual. I enjoyed it a lot but also laughed because there was so much fighting and Cannon kept winning! Seeing the very rotund William Conrad in all these scrapes was a bit surreal, that's for sure.