Barbara Gordon, the secret super hero Batgirl, has been invited to the biggest Halloween party of year. Unfortunately, she already agreed to spend the night with Robin, her younger crime-fighting partner. Instead of arguing with her mentor, Batman, Barbara decides to bring Robin along. That night, the teens arrive at the costume party, hosted by an eccentric collector of Halloween artifacts. Suddenly, all of the lights go out! When they turn on, his prized artifact, a black cat made of rare diamonds, is missing! One of the masked guests must have stolen it, and Batgirl and Robin must capture the feline felon.