Chandell, the musical virtuoso, visits Gotham City for a piano concert. But unknown to the public, Chandell is being blackmailed into a life of crime by his twin brother Harry, who retains most of the profits. Chandell intends to buy off Harry forever, and he knows just where to get the funds - from the Wayne family fortune. With Batman and Robin out of town, he suspects the robbery will be a piece of cake. However, Batman has been listening to Chandell's concert remotely, and after detecting an anomalous chord, summons Robin back to Wayne Manor to investigate.

Batman and Robin escape Chandell's trap. Once back in the Batcave, they deduce his plan to get the Wayne family fortune by killing Bruce Wayne and Dick Grayson, then marrying the rightful heir, Aunt Harriet. In order to trap the villain, Bruce and Dick fake their own deaths. However, Harry has also figured out his brother Chandell's scheme, and desiring the Wayne fortune for himself, concocts a plan to masquerade as his twin brother.