After stealing the Queen's collection of snuffboxes from a Londinium museum, Lord Marmaduke Ffogg and his sister, Lady Penelope Peasoup, escape in a thick fog. Ireland Yard calls in Batman & Robin to solve the mystery, and Barbara Gordon is eager to accompany them. The Caped Crusader is interesting in comparing Lord Ffogg's aftergrass with that of Wayne Manor. While at the Ffogg Estate, Robin learns from Ffogg's daughter, Lady Prudence that her father and her aunt, Lady Peasoup, operate a school for lady crooks under the guise of a girl's finishing school! The unimpressed Ffogg vows to steal the Crown Jewels from the Tower of Londinium.
Batman and Robin manage to bring The Batmobile and Batcomputer to Londinium (and preserve their secret identities all at the same time) by packing them into crates and passing them off as Dick Grayson's desk and books, and then reassemble them in a Batcave-like space beneath a rented manor. During The Dynamic Duo's visit at the estate with Ireland Yard Superintendent Watson, Barbara Gordon slips off to contact Alfred and have him meet her at the road leading to the estate, where she changes into her Batgirl outfit brought by the butler. Later, upon leaving the Ffogg estate, The Dynamic Duo are set upon by Ffogg's servants Scudder, Basil, and Digby (disguised as highwaymen) but are aided by Batgirl, who arrives in time to help rout the roughians - and then leaves as suddenly as she arrived! Batman and Robin return to the Londinium Batcave and are ambushed with a noxious fog bomb planted by Ffogg's servants!