A dying millionaire asks Mac, through an intermediary, to compete in a road rally. Each participant will drive one of the millionaire's classic cars. The winner gets to keep the entire collection. But someone, acting through a hired thug plans to sabotage the cars one by one. The thug gets into Mac's garage and puts sugar in the gas line of the car he's been assigned. Mac's mechanic then suggests Mac use Sally's small MG, which hasn't been seen in a couple of seasons. The intermediary accepts the new entry and the race is on. But the thug is still at work sabotaging the other cars, culminating in an accident that launches a car into a pond. The driver escapes, but his wife drowns. When the hired thug is caught, he denies having anything to do with the murder. He won't finger his contact person, though, so Mac investigates the drowning on his own -- with the killer arriving and standing lakeside with a gun, taking a shot at Mac each time he comes up for air. Can Sally (who's pregnant and showing, but her mobility isn't hampered yet) save the day?
—Peter Harris