In The Batcave, Batman's attempts to contact his junior partner in crime fighting are met with futility; alerted by Alfred about Aunt Harriet's having a fit on noticing their beds were slept in, The Caped Crusader tells him to put her at ease by saying they're spending the night at Bruce's uncle's house. Meanwhile, The Riddler's "operation" on Robin involved only the making of plaster cast from Robin's masked face, used to make a perfect "Robin" mask for Molly. After enticing The Caped Crusader with a couple of riddles, The Prince Of Puzzlers and Molly (disguised as The Boy Wonder) lead Batman on a merry chase outside the abandoned turtle mill at Orleans Cove before their vehicle is disabled by The Batray. The Riddler makes his escape as Molly tricks The Batman into taking her into The Batcave. There, our keen-eyed hero makes spots the defect in the mask caused by the straws they gave Robin through which to breathe. An unmasked Molly, after making an unsuccessful attempt to shoot Batman, makes a break for it; The Caped Crusader chases her to the top of the atomic pile (used to power The Batmobile), where she slips and falls to her dastardly death!
The Caped Crusader rescues the true Boy Wonder, but that rapacious Riddler manages to escape to The Moldavian Pavilion, where a gathering will honor the famous Mammoth of Moldavia, which is stuffed with used, yet priceless Moldavian postage stamps. The Riddler plans to steal The Mammoth, and so he drenches the pavilion with nitrous oxide, dresses in an outrageous costume and elephant mask (Holy John Merrick!) which conceals his protective gasmask, and entertains the guests with a few jokes until everyone has fallen unconscious from laughter. The Riddler and The Mole Hill Mob blast a hole through the floor and make ready to pilfer the priceless pachyderm when The Dynamic Duo leap out from inside the huge beast and subdue The Mob; whilst The Riddler runs for the rat hole and leaps into it. Batman leaps after him, and The Riddler shoots at him, misses, and hits a tank of noxious oxide causing it to explode, but not before Batman takes cover. The Riddler's body was never recovered, so it's assumable he will definitely live to plague Gotham City another day...but not if The Dynamic Duo can help it!