"Diesel" - Now there's a strange name for a young girl. Diesel is Olive Oyl's niece and she's giving her aunt a hard time about going to bed. Only when Popeye comes over and promises to tell her a bedtime "yarn" will she agree to get into her pajamas.
Popeye then tells her the story of the famous relative of his and "the Mark of Zero." We see a Robin Hood-dressed character who quickly saves a silversmith from a robbery and marks a zero on each of the bandits shirts. When the thieves go back to their boss, you know who it is -- Brutus, who wants revenge on someone interfering "with my right to free enterprise."
This was an above-average 1961 Popeye with a bunch of good lines such as Popeye congratulating himself as "Zero the Hero" or stating he can't stand "to see damskals in diskress." The different ways he repels the thugs each time are fairly clever. Brutus dressing up as one of the "damsels in distress" is funny, too.