Alfred and Robin are both convinced there's a horrible monster lurking in the Batcave. Batman thinks they're hallucinating--until he himself is attacked by something that isn't human!
Alfred comes across a 'monster' in the Wayne Manor's kitchens, only for his claims to be dismissed by Bruce. Later on, as Bruce and Jason are working in the Batcave, they encounter the 'monster' who is revealed to be Man-Bat; who's been stealing food from the kitchens.
Eager to stop the apparently-ncreasing incidents involving numerous bat-men and other creatures from Dorian's labs, Bruce & Jason change into their costumes and try to find Man-Bat and cure him with Batman's own copies of the bat-serum antidote, engaging in a fight only to find out that Man-Bat has not harmed any individuals since gaining control of his bestial side. Man-bat is then is allowed to go free as long as he continues his 'secluded lifestyle'.