Case visited Castle Frank N. Stein in search of a missing double-glazing salesman. The salesman in question turned out to be long dead and had since been revived as a monster, specifically Chuck D. Head. The detective didn't believe Chuck's side of the story, however, and proceeded to whip out his gun and pursue Chuck all over the castle, guided by a delighted Igor. At one point he was scared off by the castle sewers' resident crocodile monster, but he quickly tracked Chuck down again, clambering inside the monster's body when he retreated into his own bandages.
After Chuck was able to knock Case out, Professor Frank N. Stein attempted to modify the detective's memory through a variety of unusual methods, though wasn't sure how to fit the now heavily stretched brain back into Case's skull. Several hours later, Detective Case returned to the station, seeming quite placid, though it turned out Stein had replaced Case's brain with a grapefruit. The brain itself was still sentient and just as keen to do its duty, hoping to take the gang back to the station, though it hadn't figured out how to move yet.
What happened to Case's body and brain after these events is anyone's guess.