Bill Case is an expert bomber specialized in demolition hired by Tim Carson to take down the Applegate Mansion in hopes of building a Mini Mall to improve the town. In their first meeting, Bill accidentally set Tim's office on fire while trying to inactivate a dynamite cartridge.
Later in the film, he sneaks into the mansion and implants a powerful explosive in the building in order to blow up the place, which puts Tim's son: Chris Carson life on danger, after Chris got locked inside by school bullies.
When Tim asks him to shut down the bomb, he refuses as he believes Tim to be some Master of Disguise imposter, and takes refuge at a treetop near to the mansion waiting for the denotation. Just as he was about the detonate, Chris's teacher Sheila Fistergraff crashed her car onto the tree which caused him to trip and land right on her car.
As he was about to proceed, Tim threw the detonator away. With everything seeming to turn well at first, Bill state that the bomb was set a default, which will detonate in one minute. This forced Tim to break inside the mansion, and get Chris out to safety, leaving Chris's friend, Casper the Friendly Ghost alone to deal with the bomb. As time was almost up, Casper ate the bomb which exploded inside his stomach and saving the mansion leaving Bill in defeat.
Bill Shows a really obsessive personality, he enjoys to detonate explosives and blowing up buildings, Also it is worth to note that he behaves like a typical soldier stereotype, despite his formation, he is really clumsy.