Ilsa works at the Pterodactyl Juvenile Reformatory as a guard and cavity-searcher. At the request of her superior, Frau Ishihara, she attempts to persuade protagonist Jubei Yakyu to join the prison's baseball team by threatening to kill his new friend and fellow inmate, Suzuki Shinosuke. Jubei agrees and Ilsa is put on the team to keep an eye on things. However, Suzuki gets a little payback during this time when he uses syringes filled with a paralyzing substance to incapacitate Ilsa.After discovering what a deathtrap the baseball game has become, Jubei fakes his death and escapes. Shortly after, the paralysis wears off, and Ilsa goes after him. The two have a brief fight, and Jubei gets a little revenge of his own by showing her his own "cavity search" skills. It is here that Ilsa reveals that she is a double agent, sent to keep an eye on Ishihara at the instruction of her true boss, Governor Mifune.
Jubei is later framed by the governor for burning down the prison, killing all who remained inside. At the film's climax, he manages to track down Ilsa and the governor and kills them both with his deadly baseball pitch.