At daybreak, Batman is in the Batcave futilely trying to call Robin on their two-way radio. Alfred informs Batman that Aunt Harriet is up in arms over seeing Bruce and Dick's beds unslept in from last night; Batman tells Alfred to tell Harriet that he and Dick stayed at his uncle's house overnight.
Meanwhile, the Riddler's "operation" on Robin involved only the making of a plastic surgery cast from Robin's masked face, used to make a perfect "Robin" disguise for Molly. Riddler tricks Robin into calling police headquarters and tells Commissioner Gordon he needs to talk to Batman on the hotline, but when Batman answers Riddler grabs the phone and entices him with two more riddles on how to find Robin:
- "What kind of pins are used in soup?" (Terrapins)
- "What was Joan of Ark made of?" ("Maid of" Orleans)
Batman figures out that Riddler means the abandoned Turtle Mill at Orleans Cove and races there in the Batmobile. Molly turns on Robin's homing transmitter, and Batman quickly homes in on the signal coming from a Rolls Royce going the other way on the road, and which Riddler and Molly are driving. Batman quickly turns around and catches up with them and fires the Bat-Ray disabling the engine. The car crashes, and Riddler makes his escape as Molly tricks Batman into taking her into the Batcave.
Once there, Molly draws her gun, but Batman knew it was Molly all the time. He reveals that he immediately spotted the defects in the mask caused by the straws they gave Robin through which to breathe, and then when Molly tries futilely to shoot Batman, he reveals that when she wasn't looking he burned off the gun's firing pin with a hidden laser beam. Having failed in her murderous mission, Molly tries to escape by climbing on the scaffolding over the atomic pile (used to power the Batmobile). She quickly becomes terrified, and Batman climbs up to rescue her, but her tenuous grip gives out and she falls to her death in the pile. Batman then laments over her demise saying, "Poor deluded girl. If only she'd have let me save her. What a terrible way to go-go".
At police headquarters, Batman, Gordon and O'Hara listen to the recording made of the phone conversation between Batman, Robin and the Riddler. Gordon and O'Hara are convinced that the recording is useless, but Batman pays more attention to the background noise- a subway train passing by. Batman gets a timing on the recording and a complete train schedule from which he gets the real location where Riddler is holding Robin. Batman blasts in and rescues Robin, but Riddler and the Mole Hill Gang again manage to escape. Robin shares with Batman some things he overheard from Riddler: two more riddles:
- "How many sides does a circle have?" (Two. Inside and outside.)
- "What President of the United States wore the biggest hat?" (The one with the biggest head.)
Robin thinks Riddler is going to break into the skyscraper head office of the Gotham City National Bank, and that Riddler and his gang will go inside and cart the money outside. Batman calls Commissioner Gordon who sends a group of police to the bank skyscraper. But Riddler is actually going back to the Moldavian Pavilion at the Gotham World's Fair, where a gathering will honor the famous Mammoth of Moldavia, which is adorned with jewels on the outside and stuffed with priceless postage stamps inside. The Riddler intends to steal the mammoth, so he saturates the pavilion's ballroom with nitrous oxide (laughing gas), then dons an elephant mask over his gas mask and entertains the guests with a few one-liners until they have all fallen unconscious from the gas.
On Riddler's signal, the Mole Hill Mob blasts a hole through the ceiling of the floor below and climb up into the ballroom, and are about to pilfer the priceless pachyderm when Batman and Robin leap out from inside of it. A free-for-all ensues and the Dynamic Duo defeats the mob, but Riddler attempts to escape through the hole in the floor with Batman in hot pursuit. Armed with a gun, Riddler warns him away, but when Batman throws another flash pellet at him, Riddler misfires and ruptures one of the gas tanks instead, causing the gas to ignite, but not before Batman takes cover.
The lawsuit against Batman was dismissed as Riddler failed to show up in court. Dick is certain that the exploding gas tank took Riddler out, but Bruce points out that Riddler's body was never found. Dick begins to think they failed, but Bruce reminds him that they put the Mole Hill Mob behind bars and the Moldavian Mammoth is safe, but then Bruce reveals his one regret from the whole adventure: his failure to save Molly...
The end where Riddler disappears in the explosion is similar to the first Riddler Comic where Riddler tried to kill the Dynamic duo with a booby trapped Riddler Maze on a dock, only for Riddler to fall off and leave no trace except for a "?" The first "Riddler" Adventure at Riddler adventure pp.88-99