The Villain Of Vapor Street The annual historical festival in Old Gotham (the original city limits, lovingly restored by a grant from Wayne Enterprises) is interrupted by Lord Marmaduke Ffogg* and his female minions. When the dynamic duo respond, Lady Penelope Peasoup cold-conks Batman with his cane, while Robin is easily overpowered by Prudence Ffogg ("I woukd never hit a lady!") Ffogg unveils a giant pipe which he uses to spread a mind-controlling fog through Gotham City. They escape, of course, and Robin gets a smooch from Prudence Ffogg while climbing the walls of a building. She then cuts the bat-rope, expecting the dynamic duo to fall to their deaths. But Alfred saves the day! Ffogg has moved on to the steam tunnels beneath Gotham City, intending to add his concoction to the very steam that heats Gotham's buildings!
*Lord Ffogg is obviously intended to be called "Marmaduke", but at one point Batman refers to him as "Lord Phineas Ffogg", which is the name I remember from the show.