Seventh episode of Lupin III Series One, titled. "A Wolf Calls a Wolf." This is the first episode of the series directed by Isao Takahata and Hayao Miyazaki, after they reunited with elder brother Yasuo Otsuka at A-Pro. This is an excellent episode, one of my favorites. It still contains the hardboiled violence of the early episodes - notice the particularly gruesome killing of a couple thugs in a cave - but begins the transition towards the funnier, more slapstick-oriented later episodes.
One thing I really enjoy about the original Lupin III is the chemistry of the four main characters. There's a tension, but also a closeness that reminds me of, of all things, Seinfeld. Seriously. This series was Seinfeld With Guns.